THE 


APPLICATIONS  OP  CHEMISTPY 


THE  ARTS 


TAKEN  FROM  THE  LECTURES  OF  PROFESSOR 
RENWICK. 


PRINTED  AT  THE  COST  AND  FOR  THE  USE  OF  THE  JUNIOR  CLASS  OF 
COLUMBIA  COLLEGE,  NEW-YORK,  1851  AND  1852. 


NE  W-YORK: 

PRINTED  BY  JOHN  F.  TROW,  49  ANN-STREET. 
1851. 


THE 


APPLICATIONS  OF  CHEMISTRY 


TO 


THE  ARTS. 


TAKEN  FROM  THE  LECTURES  OF  PROFESSOR 
RENWICK. 


PRINTED  AT  THE  COST  AND  FOR  THE  USE  OF  THE  JUNIOR  CLASS  OF 
COLUMBIA  COLLEGE,  NEW- YORK,  1851  AND  1652. 


NEW-YORK: 

PRINTER  BY  JOHN  F.  TROW,  49  ANN-STREET. 
1851. 


GQO 

"R  S,0a 


Digitized  by  the  Internet  Archive 
. in  2016- 


https ’//archive. org/details/applicationsofchOOrenw 


I. 

ACIDS  OF  COMMEECE. 


1.  SULPHURIC  ACID,  S + 30  + (H  + 0). 

Sulphuric  acid  was  originally  known  as  oil%of  vitriol ; it  was 
prepared  from  metallic  sulphates  (vitriols)  by  a high  heat.  The 
acid  thus  prepared,  was  impure ; after  the  chemical  composition 
of  the  acid  was  discovered,  it  was  attempted  to  make  it^  by  the 
direct  union  of  the  elements,  and  as  this  could  not  be  effected  by 
simple  combustion,  it  was  proposed  to  burn  the  sulphur  in  con- 
tact with  a body  abounding  in  oxygen,  and  easily  decomposed. 
The  substance  chosen  for  this  purpose  was  nitre  (Nitrate  of  Po- 
tassa),  instead  of  which  however,  the  Nitrate  of  Soda  is  now  used. 
When  this  plan  was  carried  into  practice,  it  was  not  only  found 
successful,  but  a less  quantity  of  nitre  was  required  than  appeared 
to  be  necessary  from  its  chemical  constitution.  The  proportions 
now  used  are,  one  part  of  nitre  to  eight  of  sulphur.  The  process 
was  originally  performed  in  globular  vessels  of  glass ; these  were 
expensive,  and  the  quantity  of  gas  obtained  small.  The  process 
is  now  performed  in  chambers  lined  with  sheet  lead.  Upon  this 
metal,  sulphuric  acid  and  its  vapor  have  but  little  action,  and  its 
sulphate  when  formed  is  insoluble,  and  takes  the  shape  of  a crust 
upon  the  metal.  The  form  of  the  chamber  is  slightly  inclined  to- 
wards one  corner,  and  is  covered  with  water  to  the  depth  of  three 
or  four  inches  ; the  mixture  is  placed  in  an  iron  vessel,  which  is 
mounted  on  a carriage,  and  when  the  sulphur  has  been  ignited^ 
the  carriage  is  shoved  through  a small  door  in  the  side  of  the 


p31169 


4 


ACIDS  OF  COMMEECE. 


chamber.  When  the  combustion  is  completed,  the  water  is  found 
to  contain  sulphuric  acid.  To  obtain  this  acid,  the  water  is  evap- 
orated by  heat.  The  evaporation  is  commenced  in  open  vessels 
of  lead,  but  cannot  be  completed  in  consequence  of  the  great  at- 
traction between  sulphuric  acid  and  water.  The  process  is  there- 
fore completed  in  close  vessels,  or  retorts  of  glass,  set  in  an  iron 
vessel  in  a bed  of  sand.  These  retorts  are  liable  to  break,  be- 
cause the  last  portions  of  the  vapor  of  water  collect  in  large  bub- 
bles in  sulphuric  acid.  The  risk  may  be  somewhat  lessened  by 
placing  strips  of  platinum  in  the  retort ; but  it  is  better  to  sub- 
stitute retorts  of  platinum  for  glass.  That  the  latter  have  not 
come  into  general  use,  is  owing  to  their  high  price,  but  after  al- 
lowing sufficient  profit  for  the  capital  thus  invested,  sulphuric 
acid  can  be  afforded  cheaper,  when  platinum  is  used. 

Other  improvements  have  been  made  in  the  process,  the  most 
recent  of  which  have  been  founded  upon  the  chemical  principles 
involved,  which  are  as  follows  : when  a mixture  of  sulphur  and 
nitre  is  deflagrated  in  dry  atmospheric  air,  sulphurous  acid  and 
deutoxide  of  nitrogen  are  generated,  the  latter  is  immediately 
converted  into  nitrous  acid  gas,  and  the  two  acids  remain  without 
acting  upon  each  other,  unless  moisture  be  present ; but  if  the 
air  be  mixed  with  vapor,  the  two  acids  and  water  unite  to  form  a 
white  crystalline  solid,  which  falls  into  the  water  that  covers  the 
floor  of  the  chamber.  As  soon  as  this  solid  touches  the  water  it 
is  decomposed ; the  sulphurous  acid  takes  two  equivalents  of  oxy- 
gen from  the  nitrous  acids,  is  converted  into  sulphuric  acid,  and 
the  nitrous  acid  is  converted  into  deutoxide  of  nitrogen ; this  es- 
capes in  the  form  of  gas,  and  if  it  meet  with  sulphurous  acid, 
vapor  of  water,  and  oxygen,  the  process  will  be  repeated.  Thus 
it  happens  that  no  more  of  either  nitrate  is  absolutely  necessary, 
than  is  just  sufficient  to  cause  the  process  to  begin. 

The  first  attempt  at  improvement  consisted  in  rendering  the 
process  perpetual ; for  this  purpose  the  iron  vessel  was  placed  at 
the  lower  end  of  a cylinder  of  sheet  lead,  inserted  in  the  floor  of 
the  chamber.  Beneath  the  vessel  a furnace  was  built,  in  which  a 
sufficient  heat  was  generated  to  cause  the  sulphur  to  take  fire  ; and 
as  the  sulphur  was  consumed,  a fresh  supply  of  air  was  introduced. 


ACIDS  OF  COMMEECE. 


5 


In  order  to  admit  atmospheric  air,  valves  were  arranged  for  the 
escape  of  the  foul  air  and  the  admission  of  fresh.  To  supply  the 
necessary  vapor  of  water,  a small  boiler  was  provided,  whence  steam 
flowed  continually  into  the  chamber.  The  high  price  of  nitre  led 
to  the  use  of  the  nitrate  of  soda ; but  at  present,  sulphuric  acid  is 
manufactured,  without  the  use  of  either  nitrates.  As  a substitute, 
a mixture  of  nitric  acid  and  molasses  is  placed  in  a platinum  dish, 
which  is  supported  by  an  iron  tripod  upon  the  iron  vessel  in 
which  the  sulphur  is  burnt.  By  the  action  of  these  two.  substan- 
ces, oxalic  acid  is  formed,  and  deutoxide  of  nitrogen  is  liberated. 
The  oxalic  acid  is  as  yet  of  more  value  than  the  materials  from 
which  it  is  obtained,  so  that  the  whole  cost  of  the  nitrate  is  saved. 

Besides  the  common  sulphuric  acid,  another  kind  is  manufac- 
tured in  Germany,  which  is  a solution  of  the  solid  anhydrous 
acids  {S  -j-  3 0)  in  the  liquid  acid.  The  process  by  which  it  is 
manufactured  is  kept  secret.  It  is  chiefly  employed  in  dissolving 
indigo.  This  kind  of  sulphuric  acid  might  be  prepared  in  the 
following  manner  : expose  protosulphate  of  iron  to  a heat  suffi- 
cient to  drive  off  its  water  of  crystallization ; place  the  powder 
in  a retort,  and  expose  it  to  a heat  sufficient  to  decompose  it ; 
pass  the  vapor  through  vessels  containing  the  common  acid. 

Sulphuric  acid  is  perhaps  the^most  important  of  all  substances 
in  the  chemical  arts.  By  means  of  it  nearly  all  the  other  acids  are 
prepared,  and  by  its  action  a great  number  of  other  substances  are 
obtained.  The  raw  material,  although  obtained  in  large  quanti- 
ties from  metallic  sulphurets,  is  chiefly  furnished  from  Naples 
and  Sicily ; the  government  of  which  countries  possesses  a con- 
trol over  the  arts  of  others,  and  a change  in  the  manner  of  dis- 
posing of  it  was  nearly  the  cause  of  war  between  France  and 
England. 


2.  NITBIC  ACID.  N + 5 0 + (0  + H). 

Nitric  acid  has  long  been  prepared  from  sulphur  and  nitre  in 
glass  vessels.  To  obtain  it  in  larger  quantities,  the  nitre  was  decom- 
posed by  means  of  the  alumina  contained  in  clay,  in  large  earthen 


6 


ACIDS  OF  COMMEECE. 


vessels.  At  present,  nitric  acid  is  prepared  by  the  action  of  the 
two  first-named  substances,  in  an  apparatus  of  the  following  de- 
scription. Open  cylinders  of  iron  are  built  into  walls,  by  means 
of  which  a furnace  is  formed  ; each  cylinder  is  provided  with  two 
heads  of  cast-iron ; these  heads  have  passages  formed  in  them  in 
an  inclined  position  ; one  of  the  heads  being  set  in  its  place,  the 
condensing  apparatus  is  connected  with  the  passage.  The  cylin- 
der is  then  charged  with  nitre,  and  the  other  head  is  inserted. 
To  the  passage  in  the  latter  head,  a leaden  funnel,  whose  tube  is 
bent  into  three  branches,  is  adapted ; this  funnel  serves  for  the 
introduction  of  the  sulphuric  acid.  The  condensing  apparatus 
is  composed  of  a number  of  three-necked  bottles  ( Chemistry,  p.  166). 
Water  is  placed  in  only  one  of  these  vessels,  because  nitric  acid 
has  the  liquid  form ; in  order  that  the  acid  shall  be  free  from 
nitrous  acid  gas,  an  excess  of  nitre  should  be  used. 

The  prepared  nitric  acid  may  contain  some  of  the  sulphuric 
acid,  and  if  the  nitre  be  not  pure,  muriatic  acid  may  also  be  pre- 
sent. Sulphuric  acid  may  be  separated  by  nitrate  of  baryta ; mu- 
riatic acid,  by  nitrate  of  silver ; pure  nitric  acid  remains. 


3.  MURIATIC  ACID.  Ch  + H. 

Muriatic  acid  was  also  prepared  on  a small  scale  in  glass  ves- 
sels. It  is  at  present  prepared  in  an  apparatus  composed  of  iron 
cylinders,  and  three-necked  bottles,  similar  in  general  character  to 
that  used  in  the  manufacture  of  nitric  acid. 

The  solid  material  is  common  salt,  the  liquid  material  sul- 
phuric acid.  The  three-necked  bottles  contain  water. 

The  purest  acid  is  found  in  the  middle  bottles  of  the  series. 
Those  nearest  to  the  distilling  apparatus  contain  some  sulphuric 
acid  ; and  those  most  distant  contain  a weak  acid,  which  is  used 
in  a subsequent  process  for  filling  a part  of  the  bottles.  The 
residuum  of  the  manufacture  of  these  two  acids  is  sulphate  of 
soda.  This  is  now  employed  in  the  manufacture  of  carbonate  of 
soda ; and  the  quantity  of  the  latter  subtance,  which  is  required 
in  the  arts,  is  so  great  that  the  process  last  described  is  often 


ACIDS  OF  COMMEECE. 


7 


carried  on  for  no  other  purpose  than  to  obtain  the  sulphate  of 
soda.  In  this  case  the  muriatic  acid  is  not  collected,  but  is  con- 
densed in  a subterranean  passage  through  which  a stream  of 
water  flows. 


4.  PYEOLIGNOUS  ACID. 

Pyrolignous  acid  is  prepared  by  the  distillation  of  wood  in 
iron  cylinders.  Charcoal  is  left  in  them ; and  this  process  is 
often  connected  with  the  manufacture  of  gunpowder,  for  which 
this  charcoal  is  peculiarly  adapted.  The  decomposition  of  wood, 
besides  condensible  matter,  furnishes  the  gaseous  compounds  of 
carbon  and  hydrogen ; and  these  are  conveyed  from  the  condens- 
ing apparatus  to  the  furnace,  where  they  burn  and  thus  serve  as 
fuel.  The  condensing  apparatus  is  on  the  principle  of  Woolf’s  ; 
but  is  composed  of  wooden  vessels,  connected  by  wooden,  pipes. 
In  these  the  acid  is  collected,  being  a combination  of  water, 
acetic  acid,  and  several  liquid  carburets  of  hydrogen,  which  are 
rendered  capable  of  mixing  with  the  water  by  that  acid.  Pyro- 
lignous acid  is  used  in  its  original  state  in  preserving  meat ; it 
is  also  employed  as  a source  of  acetic  acid,  which  in  its  turn,  is 
converted  into  a substitute  for  vinegar.  For  the  process  in  which 
acetic  acid  is  prepared,  see  Chemistry,  p.  318. 

To  make  vinegar,  the  concentrated  acetic  acid  is  mixed  with 
sixteen  parts  of  water  and  one  of  alcohol. 


II. 

HYDEOGEN. 


1.  AEROSTATION. 

Balloons  were  originally  filled  with  heated  air,  a supply  of 
which  was  kept  up  by  a fire  of  straw.  They  are  now  filled  with 
hydrogen  gas. 

The  joint  weight  of  the  balloon  and  the  hydrogen  gas  it  con- 
tains, may  be  so  much  less  than  that  of  an  equal  bulk  of  atmos- 
pheric air  that  the  vessel  will  not  only  rise,  but  carry  a consider- 
able weight  with  it.  Gold-beaters’  leaf  may  be  used  to  make 
balloons  of  a small  size. 

Balloons  of  larger  size  are  made  of  silk,  rendered  impervious 
to  air  by  a varnish  (India-rubber  varnish). 

The  silk  is  cut  into  gores,  which  are  sewed  together ; the 
balloon,  when  distended,  has  the  shape  of  a sphere  or  spheroid. 
One  point  of  each  gore  being  cut  off,  a circular  opening  is  left 
in  the  upper  part.  At  the  other  end,  the  gores  are  produced  in  the 
form  of  ribbon-shaped  strips ; and  these,  when  sewed  together, 
form  a tube.  To  the  circular  opening  is  adapted  a valve,  made 
by  stretching  silk  over  a hoop  of  rattan  or  whalebone.  Atmos- 
pheric air  is  removed  from  the  balloon  by  compressing  it ; the 
balloon  is  filled  from  a gasometer,  which  is  usually  constructed 
by  inverting  one  wooden  tube  within  another.  The  hydrogen  is 
usually  prepared  by  the  action  of  a dilute  sulphuric  acid  on  iron 
filings.  The  latter  substance  is  placed  in  barrels,  which  are  then 
closed  by  heads.  In  each  head  are  inserted  two  pipes.  One  of 
these  has  a funnel  at  the  top,  and  reaches  nearly  to  the  bottom 
of  the  barrel ; the  other  barely  enters  the  barrel,  and  is  long 


HYDEOGEN. 


9 


enough  to  re^ch  the  gasometer.  The  first  pipe  serves  for  the  in- 
troduction of  the  dilute  acid ; through  the  second,  the  gas  flows 
to  the  gasometer.  The  barrels  are  usually  arranged  in  the  form 
of  a circle. 

The  gas  is  made  to  pass  from  the  gasometer  to  the  balloon, 
through  the  flexible  tube ; and  while  the  gas  is  flowing  into  the 
tube,  the  upper  valve  must  be  fastened  down.  The  upper  part 
of  the  balloon  is  covered  by  a network  of  cords  susceptible  of 
taking  the  shape  of  a hemisphere  or  hemispheroid,  and  from 
what  may  be  styled  the  equator,  a number  of  ropes  proceed; 
to  which  a basket  called  the  car  is  tied.  The  upper  valve 
is  loosened  after  the  balloon  is  filled,  and  is  afterwards  man- 
aged by  means  of  two  ropes  which  reach  to  the  car.  If  the 
balloon  is  full  of  gas,  it  is  necessary  to  leave  the  flexible  tube  open 
while  the  balloon  is  rising,  in  order  to  prevent  the  balloon  from 
being  burst  by  the  expansion  of  the  gas.  When  the  balloon 
reaches  its  utmost  height,  this  tube  is  closed  by  twisting  it  into 
a knot.  In  order  to  descend,  the  upper  valve  is  opened  and  a 
part  of  the  hydrogen  permitted  to  escape.  In  order  to  rise  again^ 
the  balloon  is  furnished  with  ballast  in  the  form  of  sand  tied  in 
bags,  and  a part  of  this  ballast  is  thrown  out.  The  aeronaut, 
^erefore,  has  the  power  of  ascending  and  descending  within  the 
lipits  of  the  quantity  of  gas  and  supply  of  ballast.  No  efficient 
mipans  have  yet  been  contrived  by  which  a balloon  can  be  moved 
in;  a horizontal  direction. 


USES  AND  PUEIFICATION  OF  WATEE. 


'ater  is  never  found  pure  in  nature.  It  may  either  contain 
insoijible  impurities,  which  produce  a visible  muddiness,  or  solu- 
ble Impurities.  The  latter  may  be  either  solid,  or  gaseous. 
GraseAus  impurities  are  not  always  objectionable  ; and  when  they 
are  restricted  to  oxygen  and  carbonic  acid,  their  presence  is  abso- 
lutely , necessary  to  render  the  water  potable,  and  its  quality 
wholes(|me.  The  gases  which  arise  from  putrescent  water,  are 
unwholesome.  These  may  be  removed  by  boiling.  As  this  how- 


10 


HYDKOGEN. 


ever  renders  water  disagreeable  to  the  palate,  in  a country  where 
the  necessity  for  thus  purifying  it  exists,  they  added,  many  ages 
since,  the  leaf  of  an  indigenous  plant,  which  rendered  the  water 
palatable  after  it  was  boiled.  And,  in  this  necessity,  we  have 
the  origin  of  tea.  Boiling  also  destroys  the  life  of  the  animal- 
culae  which  abound  in  stagnant  water. 

Insoluble  impurities  will  settle  when  water  is  permitted  to 
remain  at  rest.  The  deposit  may  be  accelerated  b}^  placing  a 
lump  of  alum  in  the  bottom  of  a vessel.  The  alum  dissolves  so 
slowly  and  its  solution  is  so  dense,  that  the  upper  part  of  the 
water  will  not  acquire  any  taste.  The  best  form  of  vessel  for 
this  purpose  is  that  of  a sugar-loaf. 

Water  may  be  more  rapidly  clarified  by  filters:  and  when 
the  water  is  offensive,  the  filters  should  be  in  part  composed  of 
charcoal. 

Some  waters  containing  soluble  salts  and  gases,  are  entitled 
mineral ; but  these  are  never  purified. 

Common  spring  water  may  contain  smaller  quantities  of  solu- 
ble matter,  and  this  is  chiefly  of  two  kinds — common  salt,  and 
calcareous  salts.  The  presence  of  the  first  renders  water  brack' 
ish ; the  second  makes  it  hard.  There  is  no  artificial  method 
used  for  purifying  brackish  water.  In  nature,  however,  the  sak 
appears  to  separate,  when  the  water  filters  through  a considei- 
able  thickness  of  sand.  This  indeed  is  the  only  means  of  ac- 
counting for  the  existence  of  springs  in  sand-banks. 

Hard  water  becomes  soft  and  free  from  other  soluble  impuri- 
ties, when  it  has  been  running  for  a long  time  with  a gentle  and 
steady  current.  When  the  carbonate  of  lime  is  present,  ii  is 
precipitated,  because  the  excess  of  acid  escapes,  and  the  sulplate 
of  lime  is  converted  into  the  carbonate.  Soluble  organic  bodies 
cease  to  be  soluble,  and  gases  escape.  All  the  impurities,  there- 
fore, finally  become  mechanical,  and  are  precipitated  by  rest,  or 
separated  by  filtering.  It  is  to  this  action  that  the  proverbial 
excellence  of  the  waters  of  the  Nile,  the  Ganges,  and  the  Missis- 
sippi, is  owing.  If  the  water  is  stagnant,  although  it  may  become 
soft,  it  retains  its  organic  impurities,  and  in  a more  offensive 
form  than  in  running  water. 


HYDEOGEN. 


11 


In  rocky  countries,  the  water  is  almost  always  hard,  and 
therefore  unfit  for  many  processes  in  the  arts — particularly  in 
the  woollen  manufacture,  in  bleaching,  and  in  dyeing. 

Water  has  been  rendered  soft  for  the  first  of  these  purposes, 
by  the  salts  of  ammonia  contained  in  a putrescent  animal  liquid; 
the  use  of  this  is  disgusting ; and  it  has  been  a desideratum  to  ' 
obtain  soft  water  by  a convenient  and  cleanly  operation.  The 
following  process  has  been  successfully  used  for  this  purpose. 

To  render  hard  water  soft,  take  for  one  hundred  gallons  six 
ounces  of  common  soda ; dissolve  in  one  gallon  of  soft  water  by 
boiling,  and  add  to  the  boiling  solution  two  ounces  of  white  soap. 
The  ley  will  combine  with  the  acids  of  the  soap  (organic  acids, 
see  Chemistry,  p.  321),  forming  a compound  lighter  than  water, 
which  may  be  skimmed  otf.  Thus  purified,  the  water  is  fit  for 
every  process  in  the  arts,  and  is  not  unpleasant  to  the  taste. 


3.  AMMONIA. 

The  form  in  which  ammonia  was  first  known,  was  a salt  found 
in  the  stables  of  the  Temple  of  Ammon.  It  was  probably  the 
double  phosphate  of  soda  and  ammonia.  It  is  certain,  however, 
that  common  salt  was  also  known  by  the  same  name.  The  salt 
of  ammonia  was  obtained  in  the  interior  of  Africa,  and  was 
shipped  for  Europe  from  the  port  of  Alexandria. 

When  another  article  was  brought  into  Europe  from  the 
same  port,  and  applied  to  the  same  uses,  it  went  by  the  same 
name.  This  latter  article  was  the  muriate  of  ammonia,  which  is 
still  prepared  in  large  quantities  in  Egypt.  It  is  obtained  from 
the  soot  of  chimneys,  in  which  animal  matter  is  used  as  fuel. 
The  soot  is  mixed  with  common  salt,  and  the  mixture  is  placed  in 
globular  glass  vessels,  of  which  it  occupies  about  one  half.  The 
globe  is  placed  over  a fire,  and  the  muriate  sublimes.  The  vapor 
is  condensed  on  the  upper  surface  of  the  globe  in  crystals,  which 
unite  to  form  a tenacious  mass. 

The  first  preparation  of  ammonia  in  Europe  was  known  as 
spirits  of  hartshorn,  and  was  obtained  from  the  shavings  of  horn 


12 


HYDEOGEN. 


by  destructive  distillation.  The  gas  in  the  vapor  was  condensed 
in  water,  which  became  a solution  of  ammonia  and  its  carbonate. 

A second  source  was  found  in  woollen  rags : these  are  sub- 
jected to  destructive  distillation.  The  volatile  product  is  con- 
densed ; and  is  composed  of  water  containing  ammonia  and  its 
carbonate,  with  an  animal  oil.  The  solution  is  converted  into 
muriate  of  ammonia  by  mixing  it  with  the  bittern  of  salt-works. 
A great  quantity  of  ammonia  is  obtained  at  Montfaucon,  near 
Paris,  at  an  establishment  where  horses  are  slaughtered. 

The  most  important  source  of  ammonia,  at  the  present  day,  is 
in  the  liquor  which  is  condensed  when  coal  is  distilled  for  making 
gas.  This  is  obtained  in  great  abundance,  and  it  has  been  pro- 
posed to  convert  it  into  a sulphate  by  condensing  the  mixed  va- 
por and  gas  in  sulphuric  acid. 

The  sulphate  has  also  been  prepared  by  causing  this  liquor 
to  filter  through  sulphate  of  lime.  The  sulphate  obtained  in 
either  mode  is  now  employed  in  agriculture,  and  is  the  most  im- 
portant material  in  artificial  guano.  It  has  not  yet  been  intro- 
duced in  the  arts  in  the  place  of  the  muriate,  although  there  is  no 
good  reason  to  prevent  its  being  done. 


# 


III. 

CARBON. 


• 1.  CHARCOAL. 

Charcoal  is  prepared  for  the  manufacture  of  gunpowder  in 
iron  cylinders  and  retorts,  in  the  manner  described  under  the 
head  of  Pyrolignous  Acid.  It  is  usually  prepared  in  coal-pits. 
The  wood  is  cut  into  billets  four  feet  in  length.  A stake  being 
set  up  in  the  ground,  with  a rude  cross  nailed  to  its  top,  the 
billets  are  placed  leaning  against  it  at  the  slightest  possible  in- 
clination. Other  billets  are  arranged  around  these  until  the 
diameter  of  the  base  becomes  twice  the  height  of  the  pile.  When 
a large  quantity  of  wood  is  provided,  the  heap  may  be  built  in 
two,  three,  or  even  four  layers,  with  the  same  proportion  between 
the  height  and  the  diameter  of  the  base.  The  heap  is  then  co- 
vered with  earth,  preserving  openings  for  the  admission  of  air 
and  the  escape  of  gas.  One  of  these  is  at  the  vertex  of  the  heap, 
others  around  the  base  at  equal  distances  ; and  when  the  heap  is 
composed  of  more  than  a single  layer,  holes  are  left  at  the  junc- 
tion of  the  layers.  The  central  stake  is  then  withdrawn,  and 
fire  is  set  to  the  heap  by  dropping  burning  brands  through  the 
space  which  is  thus  left.  The  combustion  extends  towards  the 
surface,  and  is  regulated  by  opening  and  closing  the  holes.  The 
hole  at  the  top  is  closed  as  soon  as  flame  makes  its  appearance 
there,  and  all  are  closed  as  soon  as  the  combustion  has  reached 
the  outward  logs.  This  is  known  by  the  earthen  cover  becoming 
red-hot.  The  heap  is  then  enveloped  in  a second  covering  of 


14 


CARBON. 


earth ; and  as  this  cracks  it  is  removed,  and  replaced  by  a fresh 
cover.  This  remains  till  the  charcoal  has  cooled.  In  this  way, 
112  lbs.  of  wood  yield  no  more  than  17  lbs.  of  charcoal.  In  the 
manufacture  of  charcoal  for  gunpowder,  1 00  parts  of  wood  de- 
composed by  the  combustion  of  12  parts  of  the  same  wood,  yield 
28  of  charcoal.  Various  plans  have  been  proposed  to  prevent  so 
great  a loss ; but  none  has  yet  been  discovered,  which  is  applica- 
ble in  the  forest. 

Where  circumstances  will  admit  of  a stationary  apparatus, 
two  methods  have  been  employed.  The  first  is  applicable  to 
resinous  woods,  in  which  the  tar  and  turpentine  are  products  of 
value.  The  apparatus  consists  in  a vaulted  chamber  of  masonry- 
on  one  side  of  which  is  a furnace,  and  on  the  opposite  side  a chim. 
ney.  The  flame  from  the  furnace,  is  directed  through  the  cham-. 
ber  to  the  chimney.  The  resin  is  collected  in  a gutter  formed  of 
brick,  in  the  floor  of  the  chamber.  In  this  way  the  product  is 
nearly  as  large  as  in  iron  cylinders. 

The  hard  woods  have  been  charred  in  kilns,  formed  in  the  ground. 
The  shape  of  these  kilns  is  that  of  an  inverted  truncated  cone,  and 
they  are  lined  with  brick.  On  the  outside  of  the  lining  several  iron 
pipes  proceed  downwards  and  enter  into  the  lower  part  of  the  kilns. 
These  serve  for  the  admission  of  air,  and  are  provided  with  stoppers 
to  regulate  the  draught.  The  cover  of  the  kiln  is  made  of  sheet  iron, 
having  as  many  short  pipes  placed  around  its  circumference  as 
there  are  long  pipes  on  the  outside  of  the  lining.  There  is  a sim- 
ilar pipe  in  the  middle  of  the  cover.  The  wood  is  laid  horizon- 
tally in  the  kiln,  and  the  cover  being  set  in  its  place,  is  loaded 
with  12  or  15  inches  of  earth.  The  fire  is  lighted  by  dropping 
fuel  through  the  central  pipe,  and  extinguished  by  closing  all  the 
pipes.  Pyrolignous  acid  may  be  collected  by  adapting  a Woolfs 
apparatus  to  one  of  the  pipes,  passing  through  the  cover.  The 
first  part  of  this  apparatus  is  an  iron  pipe.  All  the  rest  is  com- 
posed of  wood,  barrels  being  substituted  for  three-necked  bottles. 
In  this  way,  about  20  per  cent,  of  charcoal  is  obtained  from  the 
wood.  The  profitable  use  of  this  apparatus  will  depend  upon  the 
relation  between  the  expense  of  transporting  the  wood  to  the 
place  where  the  kiln  is  built  and  the  increased  profit  derived 
from  the  augmented  quantity  of  charcoal. 


CARBON. 


15 


2.  COKE. 

Coke  is  more  easily  prepared  than  charcoal. 

For  this  purpose  it  is  sufficient  to  pile  bituminous  coal  in  a 
heap,  covering  it  with  fine  coal,  and  then  with  coke  dust.  It  was 
once  considered  necessary  to  coat  the  heaps  with  straw,  and  to 
cover  the  straw  with  earth.  The  heaps  can  be  of  no  other  dimen- 
sions than  about  15  feet  in  diameter,  and  3 feet  in  height.  They 
are  ignited  by  placing  burning  coals  in  a cavity,  at  the  vortex  of 
the  heap.  The  process  requires  no  attention  whatever. 

To  obtain  large  quantities  of  coke,  prismatic  heaps  are  built, 
15  feet  wide,  3 feet  in  height,  and  of  indefinite  length.  Fire  is 
applied  at  points  distant  15  feet  from  each  other,  along  the  ridge 
of  the  heap. 

Coke  cannot  be  transported  without  great  loss.  Hence,  when 
a place  is  distant  from  coal  mines,  it  is  important  to  make  coke 
with  the  smallest  portion  of  coal.  Kilns  for  this  purpose  are  con- 
structed by  forming  a circular  chamber  of  brick,  whose  wall  is 

3 or  4 feet  high.  This  chamber  is  surmounted  by  a dome,  in  the 
middle  of  which  is  an  opening,  surrounded  by  a chimney  3 feet 
high.  An  opening  is  also  left  in  the  circular  wall  to  which  an 
iron  door  is  adapted.  The  coal  is  introduced  through  this  door 
and  the  chimney,  and  is  spread  out  to  an  uniform  depth  of  3 or 

4 inches.  Burning  fuel  is  dropped  through  the  chimney,  and  the 
door  is  left  open  until  the  combustion  is  fairly  established.  The 
door  is  then  closed,  and  the  combustion  is  finally  checked  by  lay- 
ing a fiat  stone  on  the  top  of  the  chimney. 

When  the  coal  is  of  such  a nature  as  to  burn  at  once  to  ashes, 
it  may  be  coked  by  piling  it  around  a permanent  chimney,  which 
is  circular,  and  in  building  which,  alternate  bricks  are  left  out  in 
the  two  lower  courses.  The  coal  must  be  so  arranged  that  the 
largest  pieces  shall  be  nearest  the  middle  of  the  base  of  the  heap. 

Coal-dust  may  be  converted  into  coke  by  making  it  into  a 
paste  with  water,  piling  it  into  a pyramidal  or  prismatic  form 
around  tapering  sticks,  so  disposed,  that  when  they  are  withdrawn 
they  will  afibrd  access  for  air,  and  an  escape  for  gas. 


16 


CAEBON. 


3.  LAMPBLACK. 

Lampblack  was  originally  collected  from  the  soot  of  oil 
lamps.  When  collected  on  ivory  plates,  it  was  called  ivory- 
black.  It  is  at  present  prepared  by  burning  refuse  turpentine 
in  iron  kettles,  and  directing  the  smoke  through  a cylindric 
chamber.  The  chamber  is  lined  with  blankets  or  sheepskins, 
and  has  within  it  a conical  frame  of  sheet  iron,  having  openings 
for  the  escape  of  the  heated  air.  This  conical  frame  is  suspended 
by  chains,  and  during  the  combustion  is  supported  near  the  up- 
per part  of  the  chamber.  When  the  combustion  is  completed, 
the  lampblack  is  removed  from  the  woollen  by  raising  and  lower- 
ing the  frame  of  sheet  iron. 

Instead  of  ivory-black,  animal  charcoal  is  now  usually  em- 
ployed. 

Blue-black  is  prepared  from  peach-pits.  The  article  called 
black  chalk  is  the  charcoal  of  the  holly. 

4.  ANIMAL  CHAECOAL. 

Animal  charcoal  is  chiefly  prepared  from  bones,  calcined  for 
this  purpose  in  iron  cylinders.  When  the  cylinders  are  opened, 
the  charcoal  must  be  instantly  inclosed  in  tight  iron  vessels.  It 
is  used  in  great  quantities  in  several  useful  arts  for  removing  the 
substances  which  give  taste,  smell,  and  color,  to  vegetable  pro- 
ducts. Thus  it  is  used  in  the  rectification  of  spirits,  and  in  the 
manufacture  of  sugar. 

In  sugar-making  it  is  possible,  by  the  use  of  animal  charcoal, 
to  obtain  white  sugar  at  the  first  process  from  cane-juice,  and 
molasses  may  be  rendered  as  colorless  and  transparent  as  the 
finest  syrup.  Common  charcoal  may  be  prepared  for  the  same 
purpose,  by  heating  it  with  an  alkali  until  the  fusion  of  the  lat- 
ter. The  alkali  is  then  removed  by  washing.  The  stone  which 
is  found  in  contact  with  coal,  and  is  known  as  bituminous  shale, 
may  by  charring  be  rendered  capable  of  producing  the  same  ef- 


CARBON. 


17 


feet  as  animal  charcoal,  and  makes  a more  convenient  filter. 
When  animal  charcoal  ceases  to  he  effective,  it  makes  a valuable 
manure. 


5.  MINERALOaY  OF  CAKBON. 

Species  1. — ^Diamond. 

The  diamond  is  composed  of  carbon  almost  pure.  It  usually 
occurs  in  alluvial  or  diluvial  soils.  It  is  always  crystalline,  and 
generally  retains  the  external  crystalline  form,  only  slightly 
abraded.  The  primitive  form  is  a regular  octoedron.  It  is  the 
hardest  of  all  known  substances,  is  usually  transparent,  has  the 
highest  vitreous  lustre,  and  a power  of  refracting  light  that  gives 
it  a beauty  beyond  that  of  any  other  transparent  body.  Its 
density  is  about  3 5.  In  consequence  of  their  hardness,  diamonds 
can  only  be  polished  by  their  own  powder,  and  cannot  properly 
be  said  to  be  cut.  The  cutting  of  diamonds  consists  in  opening 
out  their  crystalline  surfaces,  and  the  figure  that  can  be  given  to 
them  depends  upon  their  own  crystalline  form,  of  which,  however, 
a greater  or  less  advantage  may  be  taken  by  the  skill  of  the 
workman. 

The  forms  into  which  diamonds  can  be  cut  are  three  in 
number,  the  brilliant,  the  rose,  and  the  table.  The  brilliant  may 
be  described  by  conceiving  a regular  octoedron  to  be  deeply 
truncated  at  one  of  its  pyramidal  terminations,  truncated  to  a 
less  depth  at  the  opposite  point,  bevelled  until  the  truncations 
become  octagons,  and  bevelled  and  truncated  around  the  square 
base  of  the  two  pyramids,  until  the  number  of  faces  becomes  58. 
The  rose  diamond  has  the  same  general  form  as  the  brilliant,  but 
is  so  deeply  truncated  at  one  of  its  pyramidal  terminations  as  to 
leave  but  little  of  the  pyramid.  It  is  set  with  this  surface  lower- 
most. The  table  has  two  deep  and  equal  truncations.  Dia- 
monds are  sold  by  weight,  the  unit  of  which  is  called  a carat. 
A fine  brilliant  weighing  one  carat  is  worth  about  $40,  and  the 
value  increases  with  the  square  of  the  weight,  so  that  a brilliant 
of  two  carats  is  worth  $160. 

2 


18 


CARBON. 


Species  2. — G-raphite, 

Graphite  is  better  known  as  plumbago  or  blacklead.  It  is 
too  familiar  to  require  description.  The  finest  quality  is  found 
only  at  one  locality  in  England.  This  is  prepared  for  making 
pencils  by  sawing  it  into  strips,  which  are  set  in  sticks  of  cedar. 
In  France  pencils  are  made  by  mixing  plumbago  in  fine  powder 
with  tempered  porcelain  clay,  and  after  giving  the  mixture  the 
proper  form,  baking  it  in  a potter’s  kiln.  Pencils  of  inferior 
quality  are  made  in  G-ermany  by  mixing  powdered  plumbago 
with  melted  sulphur,  and  pouring  the  liquid  mass  into  reeds. 
The  best  graphite  gives  on  analysis  about  4 per  cent,  of  iron,  but  this 
metal  does  not  appear  to  be  an  essential  component,  and  it  may 
be  considered  as  a form  of  pure  carbon.  The  substance  called 
kish,  which  forms  on  the  surface  of  pig-iron,  has  all  the  characters 
of  plumbago  and  contains  no  iron. 

Species  3. — Anthracite  Coal. 

Species  4.— Semi-Bituminous  Coal. 

Species  5. — Bituminous  Coal. 

Variety  I. — Coking  Coal. 

Variety  II.- — Coal  that  hums  without  forming  coke. 

Species  6. — Cannel  Coal. 

Species  7. — Bitumen. 

Variety  I. — Asphaltum. 

Variety  II. — Mineral  Tar. 

Variety  III. — Tetroleum. 

Variety  IV. — Naphtha. 

6.  GAS  LiaHTS. 

Gas  has  been  obtained  for  illumination  from  bituminous  and 
cannel  coal,  from  oil,  and  from  common  rosin. 


CAEBON. 


19 


Coal  may  be  decomposed  for  the  purpose  in  cylinders  or  re- 
torts of  iron.  A number  of  these  are  built  into  the  same  furnace, 
and  the  volatile  pr.oducts  of  the  whole  are  conveyed  by  a bent 
pipe,  proceeding  from  the  top  of  each  of  them,  to  a close  horizon- 
tal channel  or  pipe,  where  the  pipes  dip  into  water  to  a small 
depth.  The  water  in  the  close  channel  serves  as  a valve,  accom- 
modating itself  to  an  unequal  flow  of  gas  from  the  several  retorts, 
and  permitting  any  one  of  the  retorts  to  be  opened  for  the  pur- 
pose of  charging  it,  without  interfering  with  the  flow  of  gas  from 
the  other  retorts.  The  gas  is  finally  collected  in  a gasometer 
(Chemistry,  p.  108),  where  it  is  stored  for  use,  but  requires  to  be 
previously  purified  on  the  following  principles.  The  volatile  mat- 
ter obtained  from  coal  may  be  either  condensible  or  gaseous. 
The  condensible  products  are:  1,  coal-tar  ; 2,  water.  The  coal- 
tar  is  of  a very  complex  constitution  {see  Chemistry,  p.  344). 
The  gaseous  products  are : 1,  ammonia,  in  much  larger  quanti- 
ties than  can  be  accounted  for  by  the  nitrogen  of  the  atmospheric 
air  enclosed  in  the  retort ; 2,  carbonic  oxide,  and  carbonic  acid ; 
3,  sulphurous  acid,  sulphuretted  hydrogen ; 4,  light  carburetted 
hydrogen,  and  olefiant  gas  (Chemistry,  pp,  168  & 169).  Of  these, 
ammonia,  carbonic  and  sulphurous  acids,  are  destructive  of  com- 
bustion ; carbonic  oxide  yields  but  little  light,  sulphuretted  hydro- 
gen, although  burning  with  a brilliant  flame,  is  offensive.  Means 
of  separating  all  except  carbonic  oxide  have  been  discovered. 
To  condense  the  coal-tar  and  water,  the  volatile  matter  is  con- 
veyed from  the  close  channel  through  a series  of  bent  pipes,  im- 
mersed in  a vessel  of  cold  water.  From  each  of  the  lower  bends 
of  the  pipe,  an  open  pipe  proceeds  downwards  nearly  to  the  bot- 
tom of  a tub  in  which  a small  quantity  of  water  is  placed.  The 
coal-tar  and  condensed  water  drop  from  the  open  pipe  into  the 
tubs,  where  the  former  occupies  the  lower  place.  The  attraction 
of  ammonia  for  water  is  so  great,  that  the  greater  part  of  that 
gas  is  condensed  with  the  water.  To  separate  the  carbonic  acid, 
the  gas  was  originally  made  to  pass  in  bubbles  through  milk  of 
lime  ; to  separate  the  sulphurous  gases,  it  was  washed  by  making 
it  pass  in  fine  streams  through  a cistern  of  water.  The  first  pro- 
cess has  been  improved  by  making  the  mixed  gas  pass  through  a 


20 


CARBON. 


close  vessel  filled  with  straw,  dipped  in  the  milk  of  lime.  Under 
these  circumstances,  the  hydrate  of  lime  is  found  capable  of 
condensing  the  sulphurous  gases,  and  the  washing  can  be  dis- 
pensed with.  This  is  advantageous,  because  olefiant  gas  is  solu- 
ble in  water,  and  a part  of  this,  the  most  valuable  of  all  the  pro- 
ducts, was  thus  lost. 

To  prepare  gas  from  oil,  that  liquid  is  permitted  to  fall  in 
drops  upon  coke,  or  pieces  of  brick,  heated  in  a retort.  Rosin  is 
dissolved  in  hot  spirits  of  turpentine,  and  treated  in  the  same 
way. 

From  the  liability  of  olefiant  gas  to  decomposition  at  high 
temperatures,  it  is  of  the  greatest  importance  that  the  heat  of  the 
retorts  should  be  well  regulated.  At  too  high  a temperature, 
not  only  is  that  gas  decomposed,  but  its  volume  is  doubled,  thus 
causing  far  more  than  a double  consumption  of  gas  for  a given 
quantity  of  light. 

The  decomposition  of  oil  and  rosin,  is  more  easily  regulated 
than  that  of  coal.  Hence,  oil-gas  in  particular,  was  more  esteemed 
than  coal-gas.  At  present,  gas  is  manufactured  at  some  estab- 
lishments from  cannel  coal,  which  is  little  inferior  to  the  best 
oil-gas. 

Gas  is  distributed  to  the  consumers,  in  iron  pipes,  through 
which  it  is  forced  by  applying  a pressure  to  the  gasometers.  It 
has  also  been  condensed  into  l-15th,  or  even  l-30th  of  its  bulk, 
and  delivered  to  the  consumers  in  strong  close  vessels.  The  lat- 
ter method  has  been  found  more  costly  than  the  distribution  in 
pipes. 


IV. 

CHLORINE. 


1.  PEEPAEATION  OP  THE  CHLOEIDES. 

To  prepare  the  chloride  of  lime,  a large  retort  of  lead  is 
used.  This  retort  is  in  two  pieces ; the  upper  of  which  is  hemi- 
spherical, the  lower  nearly  cylindrical  and  of  no  great  height. 
To  unite  them,  the  lower  part  has  a groove  around  its  edge  that 
receives  the  upper  part.  This  groove  is  filled  with  water.  The 
upper  part  of  the  retort  has  three  openings,  to  one  of  which  a 
leaden  three-branched  funnel  is  adapted.  The  second  opening 
is  provided  with  a stopper,  and  through  it  the  retort  may  be 
charged  either  with  peroxide  of  manganese,  or  with  a mixture  of 
that  substance  and  common  salt.  In  the  first  instance,  muriatic 
acid  is  poured  through  the  funnel ; and  in  the  second  water,  followed 
by  sulphuric  acid.  When  muriatic  is  used,  artificial  heat  is 
necessary  from  the  beginning  of  the  process.  But  in  the  latter 
case,  heat  is  generated  by  the  mixture  of  the  water  and  acid, 
which  is  sufficient  to  drive  off  nearly  the  whole  of.  the  chlorine. 
Through  the  third  opening  an  iron  rod  is  passed,  at  the  lower 
end  of  which  is  an  iron  frame  which  serves  to  mix  and  stir  up 
the  materials  daring  the  process.  The  condensing  apparatus  is 
composed  of  several  vaulted  chambers.  In  these  chambers  a num- 
ber of  shallow  trays  are  arranged,  and  at  the  beginning  of  the 
process  only  each  alternate  tray  is  charged  with  a thin  layer  of 
hydrate  of  lime.  After  the  process  has  continued  for  a day  iti 


22 


CHLOEINE. 


suspended,  and  the  chambers  are  ventilated.  The  other  trays 
are  then  also  charged  with  hydrate  of  lime. 

At  the  end  of  forty-eight  hours,  the  trays  first  charged  are 
replaced  by  others,  and  the  process  then  proceeds  regularly. 

Various  attempts  have  been  made  to  charge  milk  of  lime  with 
chlorine.  This  would  be  advantageous,  because  lime  in  this  state 
absorbs  a much  larger  quantity  of  chlorine  than  when  dry  • but 
it  has  not  been  successfully  applied  to  large  quantities. 

Chloride  of  soda  is  usually  prepared  by  passing  chlorine,  which 
may  be  obtained  from  the  chloride  of  lime,  through  a solution  of 
carbonate  of  soda.  The  chlorine  may  be  caused  to  pass  without 
escaping  until  the  whole  of  the  carbonate  is  decomposed,  giving 
the  strongest  solution  of  chloride.  But  the  liquor  thus  prepared 
is  speedily  converted  into  a solution  of  common  salt,  and  the 
chloride  of  soda  when  properly  prepared  contains  only  half  this 
quantity  of  chlorine.  The  completion  of  the  process  is  known  by 
the  commencement  of  an  efi’ervescence  arising  from  the  escape  of 
carbonic  acid,  which  appears  as  soon  as  the  chlorine  begins  to  be 
in  excess.  When  the  chlorine  first  enters  into  the  solution  of  soda 
it  decomposes  a part  of  it,  and  the  carbonic  acid  instead  of  escap- 
ing combines  with  another  part  to  form  the  bi-carbonate.  When 
half  the  soda  has  been  thus  combined,  any  further  action  of  the 
chlorine  will  decompose  the  bi-carbonate  also,  and  the  acid  takes, 
as  has  been  stated,  the  form  of  gas.  The  chloride  of  soda  thus 
prepared,  goes  by  the  name  of  the  Liquor  of  Labarraque. 

2.  BLEACHINa. 

Bleaching  is  the  art  of  removing  the  native  coloring  matters 
which  exist  in  the  materials  employed  in  spinning  and  weaving. 
These  materials  may  be  of  animal  origin,  as  silk  and  wool,  or  vege- 
table products,  as  flax  or  cotton. 

The  bleaching  of  linen  was  originally  performed  by  repeated 
washings  in  an  alkaline  solution,  neutralizing  the  alkali  by  an 
acid,  and  long  exposure  to  light  and  air. 

The  acid  was  obtained  from  sour  milk.  In  the  exposure  to 
light  and  air,  the  article  was  spread  upon  meadows,  where  it  re- 


CHLOEINE. 


23 


mained  for  weeks  or  even  months,  being  kept  moist  by  soft 
water.  This  process,  therefore,  could  only  be  performed  in 
countries  containing  a great  extent  of  meadow  land  and  well 
supplied  with  soft  water.  For  this  reason,  the  people  of  Holland 
monopolized  the  bleaching  of  all  northern  Europe.  The  process 
was  so  slow  that  the  capital  could  not  be  turned  more  than  once 
a year. 

The  first  improvement  consisted- in  the  substitution  of  diluted 
sulphuric  acid  for  the  acid  of  sour  milk.  Subsequent  improve- 
ments were  founded  upon  an  examination  of  the  chemical  consti- 
tution of  the  coloring  matter  of  the  vegetable  substances.  The 
coloring  matter  is  made  up  of  two  parts,  an  oil  and  a resin.  The 
oil  combines  with  alkalies  to  form  a soap  soluble  in  water.  The 
resin,  by  exposure,  enters  into  the  putrefactive  fermentation,  by 
which  it  is  finally  destroyed ; but  before  it  is  completely  de- 
stroyed, the  fibres  of  the  material  will  be  impaired.  Chlorine 
decomposes  the  resin  as  soon  as  it  comes  in  contact  with  it,  and 
therefore,  when  skilfully  used,  does  not  weaken  the  vegetable 
fibre. 

Chlorine  was  first  employed  in  the  gaseous  form,  and  next  in 
its  aqueous  solution.  The  first  mode  is  objectionable  from  the 
great  space  that  is  required  ; the  second  because  muriatic  acid 
was  generated  in  the  solution.  Both  are  inconvenient,  because 
they  require  the  presence  and  attention  of  a chemical  manipulator 
during  the  process.  The  dry  chloride  of  lime  is  therefore  uni- 
versally employed  at  present.  This  article  can  be  kept  without 
loss  of  the  gas  for  many  months ; and  the  greater  part  of  that 
used  in  this  country  is  manufactured  in  Europe. 

To  bleach  cotton  yarn  the  following  baths  are  employed. 

l5^.  Alkaline  Bath. 

This  is  prepared  by  boiling  a solution  of  good  pearlash  with 
quick  lime  and  filtering.  The  yarn,  done  up  into  hanks,  is  boiled 
some  hours  in  this  bath,  and  then  rinsed  in  running  water. 

2d.  Bath  of  Chlorine. 

This  is  prepared  by  adding  chloride  of  lime  to  water  in  the 
proportion  of  two  ounces  to  each  gallon.  There  is  no  need  of 


24 


CHLOKINE. 


filtering  the  liquid,  and  it  must  not  be  heated,  as  heat  would 
drive  off  the  chlorine. 

^d.  Acid  Bath. 

This  is  prepared  by  mixing  one  part  of  sulphuric  acid  with 
sixty  parts  of  water,  and  is  also  cold.  The  article  must  not  re- 
main in  it  more  than  an  hour. 

Uh.  Soa.p  Bath. 

This  is  composed  of  white  soap  and  boiling  water.  After 
immersion  in  this  bath,  as  well  as  after  the  two  preceding,  the 
article  is  well  rinsed  in  running  water  ; finally,  the  color  is  height- 
ened by  steeping  the  article  in  water  through  which  a small 
quantity  of  cobalt  blue  is  diffused.  To  bleach  cotton  cloths,  or 
well  twisted  threads,  the  several  baths  are  repeated.  The  colors 
of  dyed  or  printed  cottons  may  be  discharged  by  the  bath  of 
chlorine. 

Flax  must  be  prepared  for  bleaching  by  steeping  it  in  water 
for  several  hours,  but  the  process  is  of  a like  character.  Hemp 
may  also  be  bleached  in  the  same  manner. 

3.  DISINFECTINH. 

Many  of  the  substances  which  arise  from  putrefying  vegetable 
and  animal  substances,  are  compounds  of  hydrogen.  They  are 
always  disagreeable  to  the  sense  of  smell,  often  unwholesome,  and 
are  sometimes  the  vehicles  of  contagious  matter.  Even  the  ex- 
halations of  a healthy  body  are  unwholesome,  and  that  of  an  un- 
healthy person  much  more  so.  The  disease  is  sometimes  propa- 
gated by  these  exhalations,  and  there  are  cases  in  which  liquids 
are  formed  in  the  body  which  may  communicate  disease  by  mere 
contact,  as  in  the  small-pox,  and  vaccine  pustules.  These  exhala- 
tions and  liquids  all  contain  hydrogen,  and  may,  as  well  as  the 
products  of  putrefaction,  be  decomposed  by  chlorine. 

Chlorine  of  course  cannot  be  employed  to  disinfect  wide  dis- 
tricts, or  even  open  and  airy  parts  of  cities,  but  may  be  success- 
fully used  in  houses,  and  closely  built  streets. 


CHLORINE. 


25 


To  disinfect  a building,  the  ventilation  is  to  be  checked  and 
chlorine  freely  liberated  within  it.  This  is  most  easily  done  by 
chloride  of  lime,  which  gives  out  the  gas  slowly  by  mere  e:^posure  ; 
more  rapidly  by  adding  small  quantities  of  water  ; and  still  more 
freely  by  pouring  on  an  acid.  Vinegar  is  the  most  convenient 
acid  for  domestic  use. 

When  a disease  is  contagious,  it  may  be  prevented  from  being 
communicated  by  washing  in  dilute  chloride  of  soda,  and  this  has 
been  found  to  be  efficacious  after  several  hours  had  intervened. 
In  the  case  of  the  plague,  a person  has  worn  with  safety  the 
clothes  of  those  who  have  died  of  that  disease,  after  they  had  been 
merely  steeped  in  chloride  of  soda  and  dried,  without  any  wash- 
ing or  other  purification. 


V. 

SILICON. 


1.  MINERALOGY  OF  SILICA. 

Species  1. — Quartz. 

Silica  is  found  nearly  pure  in  quartz  and  flint.  Quartz  is 
always  crystalline.  The  primitive  form  is  a rhomb,  the  most 
usual  external  figure  a six-sided  prism — terminated  by  six-sided 
pyramids.  The  prism  often  disappears,  and  only  one  of  the  ter- 
minations is  visible  in  most  other  cases.  Quartz  is  hard  enough 
to  scratch  glass ; it  is  infusible  by  the  mouth  blowpipe,  with  the 
exception  of  one  of  its  varieties ; it  may  be  transparent  and  color- 
less, in  which  case  it  is  called  rock-crystal ; when  white  and  opaque 
it  is  called  milk  quartz.  It  is  frequently  colored  by  metallic  ox- 
ides without  losing  its  transparency.  When  the  colors  are  yel- 
low, brown,  or  smoky,  it  is  called  cairngorm,  and  is  used  by  the 
lapidary.  When  of  a violet  color  it  has  been  called,  but  im- 
properly, amethyst ; when  the  opaque  variety  is  tinged  with 
crimson  it  is  called  rose  quartz.  In  one  variety  the  quantity  of 
oxide  of  iron,  which  is  present,  renders  it  fusible — from  its  color 
this  is  called  ferruginous  color ; and  when  in  handsome  crystals, 
of  high  lustre,  it  is  used  as  a gem  under  the  name  of  hyacinth  of 
compostella.  The  lustre  of  quartz  is  vitreous,  and  its  fracture 
conchoidal. 

Species  2. — Flint. 

Flint  is  opaque,  and  has  a conchoidal  fracture. 


SILICON. 


27 


Species  3. — Opal. 

Silica,  combined  with  water,  forms  a species  of  minerals  which 
is  distinguished  by  a resinous  lustre.  When  these  are  transpa- 
rent, or  translucent,  they  go  by  the  name  of  opal.  The  precious 
opal,  emits  from  its  interior  a play  of  the  prismatic  colors,  a pro- 
perty called  opalescence.  The  fire-opal  reflects  flashes  of  orange- 
- colored  light.  The  common  opal  has  no  internal  reflection,  but 
is  translucent ; while  menilite  is  opaque,  and  of  a dark-gray 
color. 

» 

Species  4 and  5. — Chalcedony  and  Jasper. 

Silica,  combined  with  a small  quantity  of  alumina,  forms  chal- 
cedony and  jasper.  The  first  of  these  is  translucent,  the  second 
opaque.  Both  may  derive  various  colors  from  metallic  oxides, 
and  jasper  is  most  frequently  colored  brownish-red  by  oxide  of 
iron.  When  jasper  and  white  chalcedony  occur  in  parallel  layers, 
the  compound  is  called  onyx,  and  was  much  used  by  the  ancients 
in  making  the  gems  called  cameos.  Modern  cameos  are  usually 
made  of  a shell  found  in  the  Bed  Sea,  the  inner  layers  of  which 
are  red  and  the  outer  layers  white.  Chalcedony  of  various  colors, 
arranged  with  other  silicious  minerals  in  bands  or  concentric 
layers,  goes  by  the  name  of  agate.  Some  of  these  are  used  by 
the  lapidary,  and  others  are  of  sufficient  beauty  to  be  employed 
as  gems.  One  description  of  agate  exhibits  arborescent  crystals, 
and  is  known  as  moss-agate  or  mocha  stone.  The  same  mineral, 
when  of  a pale-red  color,  is  called  cornelian.  The  sard,  which 
is  of  a fine  red  color,  may  also  be  considered  as  a variety  of  chal- 
cedony, and  forms  with  a white  variety  the  sardonyx. 

Among  other  silicious  minerals  is  horn-stone,  which  has  a 
strong  resemblance  to  flint,  with  the  exception  that  it  is  translu- 
cent and  has  a splintery  fracture,  like  that  of  horn. 

Species  6. — Felspar. 

The  silicates  are  exceedingly  numerous.  Among  them  are  the 
felspars,  which  are  all  silicates  of  alumina  and  an  alkali,  fre- 


28 


SILICON. 


quently  containing  also  an  alkaline  earth.  Common  felspar  is  a 
silicate  of  alumina,  potassa,  and  lime.  It  is  generally  crystal- 
lized, having  for  its  primitive  form  an  oblique  rectangular  prism. 
The  secondary  forms  are  very  numerous,  and  most  of  them  are 
oblique  prisms  differing  in  the  number  of  sides.  The  lustre  of 
felspar  is  usually  vitreous ; but  there  is  one  variety  so  much  so 
that  it  has  a direct  resemblance  to  common  glass. 

Another  variety  of  felspar  has  a pearly  lustre,  and  is  called 
adularia. 

Albite  is  a silicate  of  potassa,  soda,  and  lime.  Its  primitive 
form  is  a doubly  oblique  prism,  its  color  white.  It  has  less 
lustre  than  common  felspar,  with  which,  however,  it  was  long 
confounded. 

The  Labrador  felspar  is  opalescent.  It  was  originally  found 
as  pebbles,  on  the  shores  of  that  country.  It  has  more  recently 
been  discovered  in  place,  and  in  large  quantities  in  the  Adirondac 
Mountains.  Some  forms  of  felspar  decompose  spontaneously, 
and  after  being  transported  by  water,  become  porcelain  clay — the 
kaolin  oi  the  Chinese, 

Species  7. — Mica. 

Mica  is  also  a silicate  of  alumina  and  potassa,  in  which  the 
proportion  of  silica  is  less.  It  is  infusible,  and  occurs  in  masses 
made  up  of  thin  plates,  into  which  it  can  be  drawn  almost  with- 
out limit.  These  plates  are  the  cleavages  of  crystals  whose  primi- 
tive form  is  a rhomb,  and  most  usual  external  figure  a regular 
six-sided  prism.  The  plates  are  fiexible  and  elastic,  usually 
transparent  and  sometimes  colorless.  When  colorless  it  is  used, 
in  some  parts  of  Russia,  instead  of  glass ; and  we  employ  it  in 
the  front  of  stoves.  When  opaque,  it  may  be  white,  yellow,  or 
bronze-colored,  and  has  a metallic  lustre,  so  that  it  is  frequently 
mistaken  for  metallic  ores. 

Species  8. — Talc. 

Tale  is  a silicate  of  magnesia  and  potassa,  and  has  the  same 
structure  as  mica.  It  is  however  unctuous,  and  the  plates  al- 


SILICON. 


29 


though  flexible  are  not  elastic.  When  compact,  it  is  used  by  the 
Chinese  in  statuary.  When  granular  and  of  a dark  color,  it  is 
used  in  some  parts  of  France  for  cooking  vessels.  When  com- 
pact and  sufficiently  friable  to  make  a mark,  it  is  called  French 
chalk.  The  same  substance,  mixed  with  grains  of  silica,  is  our 
soap-stone. 

Sulphate  of  lime  occurs  in  transparent  sheets,  like  mica  and 
talc ; but  it  is  neither  flexible  nor  elastic,  and  becomes  opaque 
by  heat. 

Species  9. — Hornblende. 

Hornblende  is  a silicate  of  alumina,  lime,  and  oxide  of  iron.  It 
is  of  a dark  green,  approaching  to  black.  It  is  always  crystalline^ 
the  primitive  form  being  a rhomb.  Several  other  minerals  have 
the  same  primitive  form  and  general  composition,  with  the  ex- 
ception of  the  proportion  of  iron,  which  is  less  in  all  of  them  and 
wanting  in  one.  Hornblende  is  a constituent  of  several  rocks, 
which,  on  exposure  to  the  air,  decompose  into  a green  earth. 
These  rocks  are  hence  called  green  stones. 

Species  10. — Pyroxene. 

Pyroxene  is  a silicate  of  lime,  magnesia,  and  metallic  oxides. 
Its  primitive  form  is  a four-sided  prism,  of  very  small  obliquity. 
Its  most  usual  form  is  a six  or  eight-sided  prism,  of  which  four  of 
the  sides  are  larger  than  the  others,  with  diedral  summits.  When 
of  a black,  or  dark  green  color,  it  is  called  augite.  There  are 
several  other  sub-species,  one  of  which  is  white  and  contains  no 
metallic  oxides. 


2.  MANUFACTUKE  OF  GLASS. 

Glass  may  be  distinguished  by  the  following  names : 

1.  Soluble  glass ^ a subsilicate  of  potassa. 

2.  Crown  glass ^ a silicate  of  potassa. 

3.  French  glass^  a silicate  of  soda. 

4.  Flint  glass^  a silicate  of  potassa  and  lead. 


30 


SILICON. 


, 5.  Paste^  a silicate  and  borate  of  potassa  and  lead. 

6.  Enamel^  a silicate  and  stannate  of  potassa  and  lead. 

7.  Bottle  glass^  of  any  bases  whatever. 

Grlass  which  contains  potassa  is  liable  to  deliquesce,  and  that 
which  contains  soda  to  effervesce.  By  the  addition  of  a small 
quantity  of  lime,  both  of  these  faults  may  be  overcome.  Lime  is 
therefore  an  essential  constituent  of  the  first  six  kinds. 

The  oxide  of  arsenic  also  tends  to  render  glass  white,  and  a 
small  quantity  of  it  is  added  to  flint  glass. 

The  alkaline  substance,  except  in  the  case  of  paste,  is  always 
employed  in  the  form  of  a carbonate.  The  silicious  matter,  with 
the  same  exception,  is  sand,  and  as  this  sand  is  often  of  quartz 
colored  by  metallic  oxides,  the  same  color  would  appear  in  the 
glass.  It  has  been  found,  however,  that  the  peroxide  of  manga- 
nese, when  added  to  melted  glass,  will  sink  through  it  and  carry 
with  it  the  other  metallic  oxides.  By  the  use  of  this  substance, 
it  has  therefore  become  possible  to  substitute  common  sand  for 
pulverized  flints  in  making  the  best  kinds  of  glass. 

When  the  carbonate  of  an  alkali  is  mixed  with  sand  and 
heated,  the  carbonate  fuses ; as  soon  as  it  becomes  liquid  the 
silica  begins  to  act  upon  it,  causing  the  carbonic  acid  to  escape. 
This  gas  being  evolved  in  the  midst  of  a viscid  liquid,  causes  it 
to  swell  to  many  times  its  original  bulk  ; the  continued  applica- 
tion of  heat,  however,  will  finally  expel  all  the  gas,  and  the  mix- 
ture will  subside  to  even  less  than  its  original  bulk.  We  thus 
obtain  a silicate  of  the  alkali,  which,  however,-is  not  yet  vitreous. 
To  convert  it  into  glass  it  is  necessary  to  fuse  this  compound. 
Grlass-making  is  therefore  divided  into  two  processes,  in  the  first 
of  which  the  carbonic  acid  is  liberated,  and  in  the  second,  the 
compound  is  melted.  The  first  is  called  fritting,  the  second 
melting. 

Fritting  is  performed  in  large  ovens,  and  the  frit,  which  has 
the  consistence  of  paste,  is  cut  into  blocks  of  the  shape  and  size 
of  bricks.  Melting  is  performed  in  vessels  called  glass-pots, 
made  of  plastic  clay  mixed  with  clay  heated  until  all  the  water  is 
removed,  and  then  pulverized.  The  clay  must  be  as  refractory 
as  possible.  However  carefully  the  material  may  be  prepared 


SILICON. 


31 


and  mixed,  the  glass-pots  are  liable  to  crack  by  sudden  changes 
of  temperature,  and  hence  they  are  never  permitted  to  cool.  The 
fires  of  glass-works  continue  day  and  night  for  indefinite  periods. 
When  a glass-pot  is  to  be  replaced,  it  is  heated  red-hot  by  the 
gradual  application  of  fire  in  a separate  furnace ; the  old  pot  is 
then  removed  by  pulling  down  a part  of  the  furnace.  The  new 
pot  is  placed  upon  an  iron  carriage,  and  thus  introduced  into  the 
furnace,  which  is  rebuilt  with  brick  laid  in  tempered  clay.  When 
wood  is  employed  as  the  fuel,  the  fire,  if  well  managed,  is  free 
from  smoke.  But  when  bituminous  coal  is  employed,  it  is  ne- 
cessary to  place  hoods  upon  the  top  of  the  glass-pot. 

A ffreat  proportion  of  the  glass  articles  which  are  found  in 
commerce,  are  made  by  blowing.  This  is  performed  by  the  breath 
applied  to  an  iron  tube.  This  tube  when  introduced  into  the 
glass-pot  causes  a small  portion  of  glass  to  adhere.  If  this  tube 
be  withdrawn  and  permitted  to  cool  a little,  more  glass  will  ad- 
here, when  it  is  again  dipped.  This  is  continued  until  the  re- 
quisite quantity  of  glass  is  collected  on  the  tube.  By  blowing 
through  the  tube,  the  glass  will  be  distended  into  the  form  of  a 
hollow  vessel,  whose  figure  may  be  modified  by  its  own  weight, 
and  the  motion  of  the  tube ; a perfect  sphere  may  be  obtained  by 
holding  the  tube  horizontally  and  spinning  it  around.  A cylin- 
der terminated  by  round  ends  may  be  obtained  by  holding  the 
tube  vertically,  and  swinging  it  from  side  to  side.  A cylinder 
may  also  be  formed  by  holding  the  tube  horizontally  and  causing 
the  glass  to  revolve  on  a plain  surface.  The  first  method  is  em- 
ployed in  making  crown  glass.  When  the  sphere  has  been  blown 
into  its  full  extant,  another  workman  takes  a small  portion  of 
melted  glass  upon  a rod  and  applies  it  to  the  sphere  at  a point 
directly  opposite  to  that  where  the  tube  is  inserted  ; the  neck  is 
then  cut  off  by  means  o'f  a drop  of  water.  The  opening  is  then 
applied  to  the  point  of  a triangular  plank,  and  being  turned 
around,  takes  the  shape  of  a hollow  cone.  The  hollow  cone  is 
then  spun  around  rapidly,  and  the  glass  arranges  itself  by  the 
centrifugal  force  in  the  form  of  a round  plate,  one  of  whose  sur- 
faces is  plain,  and  the  other  has  a knob  in  the  middle  to  which 
the  rod  is  attached.  This  knob  gives  the  name  to  glass  made  in 


32 


SILICON. 


this  way,  from  its  resemblance  to  the  crowyi  of  a broad-brimmed 
hat.  These  round  plates  are  cut  into  rectangles  for  glazing. 

Window  glass  may  also  be  made  by  blowing  it  into  the  shape 
of  a phial.  For  this  purpose  the  glass  is  turned  upon  a plain 
surface,  while  in  the  act  of  blowing.  The  phial  is  made  into  a 
cylinder,  open  at  each  end  by  cutting  off  the  top  and  bottom.  It 
is  then  split  up  on  one  side,  and  the  cylinder  is  brought  into  the 
form  of  a flat  plate  by  heating  in  an  oven,  until  it  drops  by  its 
own  weight.  The  oven  employed  is  the  annealing  oven,  in  which 
all  glass  is  placed  before  it  can  be  used.  Annealing  consists  in 
bringing  it  to  a red  heat,  and  causing  it  to  cool  very  slowly.  If 
this  were  not  done,  the  glass  would  be  so  brittle  that  it  would  not 
bear  the  slightest  blow.  This  same  method  was  used  for  forming 
the  Venetian  mirrors,  and  in  the  looking-glasses  still  manufactured 
in  Bohemia.  Both  of  these  are  free  from  color,  which  depends 
however  upon  the  quality  of  the  materials — the  sand  employed 
in  both  cases  being  pure  white,  and  the  alkalies  employed  in  Bo- 
hemia being  the  best  pearlash. 

French  window  glass  is  made  of  sand,  and  barilla  or  kelp. 
Plate  glass  is  of  the  same  chemical  constitution  as  French  window 
glass,  but  the  materials  are,  1,  a colorless  sand;  2,  crystallized 
carbonate  of  soda ; 3,  white  marble.  The  plates  are  prepared  by 
casting ; for  this  purpose,  a quantity  of  glass  is  poured  into  a 
small  glass-pot  and  kept  melted  for  24  hours.  The  glass-pot  is 
then  raised  from  the  furnace  by  machinery,  so  arranged  that  it 
can  be  carried  over  the  middle  of  a large  table  made  of  bronze ; 
while  it  is  thus  carried,  it  is  tilted  so  that  the  glass  may  pour 
out.  The  stream  of  glass  is  followed  by  a roller  of  bronze,  which 
moves  upon  two  of  the  rollers  by  which  the  surface  of  the  table 
is  inclosed.  The  table  is  heated  by  a fire  made  beneath  it. 

The  plate  thus  formed  has  not  the  polished  surface  of  blown 
glass,  and  therefore  requires  to  be  polished.  In  polishing,  plate- 
glass  undergoes  three  separate  operal^ions.  In  the  first,  it  is 
rubbed  with  coarse  sand,  one  of  the  plates  being  employed  as 
the  rubber  of  another.  In  the  second,  it  is  ground  by  means  of 
fine  sand  upon  a wooden  rubber : the  sand  is  in  both  cases 
wet.  In  the  third  operation,  the  oxide  of  tin  (tutty)  is  employed. 


SILICON. 


38 


When  the  glass  has  received  its  final  polish,  it  often  exhibits 
flaws  and  stria ; therefore  it  rarely  happens  that  one  of  these 
large  plates  can  be  used  entire.  The  glass  is  then  to  be  silvered  ; 
this  is  effected  by  applying  an  amalgam  of  tin  and  mercury  to 
one  of  the  surfaces  of  the  glass.  The  tin  is  in  the  form  of  foil, 
and  the  sheet  must  be  free  from  holes  or  flaws.  The  French 
lay  the  tin  upon  the  glass,  and  pour  mercury  over  it.  The  Eng- 
lish pour  the  mercury  first  upon  the  surface  of  the  glass,  and 
apply  the  tin-foil  to  it. 

The  materials  in  flint-glass  are  the  best  sand,  pearlash,  and 
red-lead.  It  is  softer  than  the  foregoing  descriptions  of  glass, 
and  more  liable  to  break  by  changes  of  temperature.  It  possesses 
higher  lustre,  is  usually  more  free  from  color,  and  is  the  only  de- 
scri^ion  employed  in  cut  glass. 

Griass  is  cut  by  the  successive  action  of  four  wheels  revolving 
with  great  velocity,  and  dipping  in  troughs  containing  water. 
The  first  wheel  is  of  iron,  and  the  trough  contains  sand.  The 
second  wheel  is  a common  grindstone.  The  third  is  of  wood, 
and  the  trough  contains  pumice-stone.  The  fourth  wheel  is 
covered  with  felt,  and  coated  with  fine  emery  or  tutty.  Flint- 
glass  is  also  cast  in  moulds  of  copper,  which  must  be  previously 
heated.  The  surface  is  afterwards  polished  by  a succession  of 
powders  similar  to  those  employed  in  cutting.  Flint-glass  is  also 
employed  in  optical  instruments,  and  particularly  as  a part  of  the 
object-glass  of  telescopes.  The  flint-glass  thus  employed  ought 
to  contain  a greater  proportion  of  lead.  It  was  long  manufac- 
tured only  in  England.  The  English  flint-glass  for  optical  instru- 
ments was  made  by  blowing,  by  which  it  is  rendered  more  uniform 
in  structure,  and  more  free  from  flaw  than  if  it  were  left  at  rest 
until  it  became  solid.  But  it  is  difficult  to  procure  in  this  way 
pieces  of  large  size  ; and  the  largest  disks,  made  in  England,  have 
not  exceeded  six  inches  in  diameter.  In  Switzerland  and  Ger- 
many, the  disks  are  made  by  casting;  and  after  they  have  become 
cold,  they  are  set  in  a ring  of  copper  and  annealed  under  strong 
pressure.  In  this  way,  disks  sufficient  to  make  telescopes  four- 
teen feet  in  length  have  been  obtained. 

The  materials  employed  in  paste  are  rock  crystal,  precipi- 
3 


34 


SILICON. 


tated  carbonate  of  lead,  fused  borax,  and  potassa  purified  by  al- 
cohol. The  glass  is  melted  in  crucibles,  in  which  it  is  permitted 
to  cool.  The  lump  obtained  by  breaking  the  crucible  is  sawn 
into  pieces  by  means  of  soft  iron  and  emery.  This  paste  is  co- 
lorless, and  has  a high  lustre.  It  is  employed  to  imitate  the 
diamond  ; and  the  imitation,  by  candle-light,  is  very  good. 
When  colored,  by  being  fused  with  metallic  oxides,  it  may  be 
used  to  imitate  other  gems.  The  art  is  therefore  restricted. 
The  most  difficult  of  all  the  gems  to  imitate,  is  the  ruby.  The 
coloring  matters,  used  in  making  paste,  are  now  employed  in  the 
manufacture  of  flint-glass;  some  specimens  of  which  are  composed 
of  layers  of  different  colors.  By  grinding  away  a part  of  either, 
the  other  is  exposed. 

To  prepare  enamel,  lead  and  tin  are  fused  together,  an4  ex- 
posed to  a current  of  air  until  both  are  oxidated.  This  combina- 
tion is  fused  with  good  crown-glass.  The  mixture  is  nearly 
opaque  and  white.  It  may  be  colored  by  fusing  it  with  metallic 
oxides. 

Enamel  is  used  in  the  two  arts  of  painting — in  enamel  and 
in  mosaic.  To  paint  in  enamel,  no  other  colors  are  necessary 
than  white,  black,  red,  yellow,  blue,  and  a neutral  gray. 

The  colors  are  ground  with  gum,  and  applied  like  water-co- 
lors. For  staining  glass,  they  may  be  ground  with  oil  and  diluted 
with  spirits  of  turpentine.  The  principle  of  painting  is  the 
same  as  in  oil.  The  colors  are  applied  in  the  inverted  order  of 
their  fusibility ; and  after  each  has  been  applied,  it  is  placed  in  a 
furnace  where  it  is  vitrified. 

To  paint  in  mosaic,  as  many  shades  of  color  must  be  pro- 
vided as  exist  in  the  original  picture.  These  colors  are  broken 
into  fragments,  and  are  applied  to  a bed  of  plaster.  After  the 
whole  surface  is  covered,  it  is  reduced  to  a uniform  level  and 
polished.  In  the  establishment  at  Borne,  17000  different  shades 
of  colors  have  been  accumulated. 

The  Florentine  mosaic  is  made  by  setting  pieces  of  colored 
glass,  or  gems,  in  slabs  of  marble. 

Under  the  head  of  glass  is  to  be  ranked  the  porcelain  of 
Beaumur.  This  is  prepared  by  bedding  glass  in  sand,  and  heat- 


SILICON. 


85 


ing  it  to  redness.  A part  of  the  alkali  is  driven  off  and  com- 
bines with  the  sand.  The  glass  thus  loses  its  transparency  and 
much  of  its  fusibility,  while  it  becomes  harder  and  less  brittle. 
When  crown-glass  is  treated  in  this  way,  it  makes  excellent  ves- 
sels for  chemical  purposes ; and  when  flint-glass  has  the  sand  in 
contact  with  only  one  of  its  surfaces  it  becomes  opaque  only  on 
that  side,  and  retains  its  vitreous  appearance  on  the  other. 


YI. 

ALUMINUM. 


1.  MINERALS  OF  ALUMINA. 

Species  1. — Corundum. 

Alumina  is  found  nearly  pure  in  minerals  to  which  the  generic 
name  of  Corundum  may  he  given.  This  mineral  occurs  in  crys- 
tals, whose  primitive  form  is  a rhomb,  and  whose  most  usual  form 
is  a very  acute  triangular  dodecahedron.  Corundum  is  harder 
than  any  other  substance,  except  the  diamond.  It  is  sometimes 
colorless  and  transparent,  with  high  vitreous  lustre.  This  variety 
is  used  in  jewelling  clocks  and  watches.  When  it  is  transparent 
and  of  a fine  red  color,  it  is  the  oriental  ruby ; when  blue,  sap- 
phire ; when  green,  the  oriental  emerald ; and  when  violet,  it  is  the 
true  amethyst.  It  is  sometimes  opaque,  or  merely  translucent, 
when  it  is  of  no  value  except  to  be  crushed  into  emery. 

Species  2. — Emery. 

Emery  is  a fine-grained  corundum,  which  occurs  in  the  island 
of  Naxos,  &c.  Emery  is  crushed  and  sorted,  and  used  in  grind- 
ing and  polishing,  being  capable  of  cutting  every  substance  ex- 
cept the  diamond. 

The  Gribbsite  is  a hydrate  of  alumina  found  only  at  Rich- 
mond, Mass.  The  Wavelite  which  was  supposed  to  be  a hydrate, 
contains  fiuoric  acid. 

Species  3. — Turquoise. 

The  turquoise  is  a hydrate  of  alumina,  covered  by  oxide  of 


ALUMINUM. 


37 


copper ; there  is  also  a turquoise  which  is  a fossil,  and  is  colored 
by  carbonate  of  copper. 

Species  4. — Spinelle. 

Spinelle  is  a compound  of  alumina  and  magnesia.  It  is  dis- 
tinguished by  its  crystalline  form,  which  is  a regular  octaedron  ; 
when  transparent,  and  colored  red  by  chrome  acid,  it  is  valued 
as  a gem  and  bears  the  name  of  oriental  ruby.  It  is  more  fre- 
quently opaque,  and  colored  by  metallic  oxides.  There  is  a com- 
pound of  alumina,  magnesia,  and  oxide  of  zinc,  which  has  the  same 
crystalline  form,  and  is  called  Automalite. 

Species  5. — Garnet. 

Garnet  is  a silicate  of  alumina,  and  metallic  oxides  ; of  these 
the  protoxide  of  iron  is  sometimes  in  such  quantity  that  the  min- 
eral is  magnetic.  The  structure  is  always  crystalline  ; the  prim- 
itive form  being  the  rhombic  dodecahedron.  This  is  one  of  the 
most  usual  forms,  and  another  frequent  form  is  a solid  bounded 
by  24  irregular  faces.  When  transparent,  and  of  a red  color  it 
is  employed  as  a gem.  Large  garnets  were  much  valued  by  the 
ancients  under  the  name  of  Carbuncle. 

Species  6. — Slate. 

Slate  is  a silicate  of  alumina.  In  roof  and  writing  slate  the 
alumina  preponderates. 

There  is  another  description  in  which  silica  preponderates  to 
such  a degree  that  it  will  strike  fire  with  steel,  and  one  of  its 
forms  is  used  as  a whetstone.  Another  called  basanite  or  Lydian 
stone,  is  employed  to  test  the  quality  of  gold. 

Species  7. — Clays. 

All  the  clays  are  compounds  of  silica  and  alumina.  That 
which  is  called  china-clay,  is  formed  by  the  decomposition  of  fel- 
spar, and  the  loose  matter  being  transported  by  water  loses 
the  alkali.  Blue  clay  is  colored  by  protoxide  of  iron,  and  red 


88 


ALUMINUM. 


clay  by  the  peroxide.  Both  of  these  have  been  generated  by 
the  decomposition  of  hornblende. 


2.  POTTEKY. 

Pottery  may  be  divided  into  the  following  kinds : 

1.  — Brick  and  Tile. 

2.  — Red  and  Black  Ware, 

3.  — Stone  Ware. 

4.  — Delft  Ware. 

5.  — Queens  Ware. 

6.  — Porcelain  Ware. 

7.. — Wedgewood. 

8. — Crucibles. 

1.  Brick  and  tile,  inay  be  made  of  any  description  of  clay. 
In  the  United  States  that  which  burns  of  red  color  is  preferred. 
In  making  brick,  when  the  clay  contains  too  large  a proportion 
of  alumina,  it  is  tempered  with  common  sand.  The  tempering 
is  now  performed  by  means  of  machines  ; the  simplest  and  most 
efficient  of  which  is  composed  of  a vertical  shaft,  around  which  a 
number  of  iron  blades  are  placed  in  the  form  of  a screw.  This 
screw  is  usually  turned  by  horses,  and  not  only  mixes  the  clay, 
sand,  and  water,  but  forces  the  mixture  from  the  bottom  of  a tub 
in  which  the  screw  works.  As  the  mixture  issues,  it  is  received 
in  moulds.  These  are  open  frames  of  wood,  placed  upon  a plank. 
The  clay  is  pressed  into  these  moulds,  and  the  excess  removed  by 
means  of  a roller  or  scraper.  The  brick  is  then  laid  upon  a level 
earthen  floor,  covered  by  a shed,  where  it  dries  until  it  becomes 
sufficiently  firm  to  be  handled.  It  is  then  piled  in  the  manner  of  a 
wall,  hollow  and  with  the  greatest  practicable  amount  of  empty 
space.  When  it  has  dried  in  this  position  as  much  as  it  can  by 
exposure,  it  is  removed  to  the  kiln  in  which  it  is  burnt. 

The  kiln  may  be  either  temporary  or  permanent. 

The  temporary  kilns  are  formed  by  building  walls  and  arches 
of  soft  bricks,  which  serve  as  fire-places  and  flues.  Upon  these 
arches  the  dried  bricks  are  piled  in  courses,  with  the  largest  at- 


ALUMINUM. 


39 


tamable  space  between  the  several  bricks.  The  outside  of  the 
kiln  has  the  shape  of  a truncated  pyramid,  and  is  inclosed  by 
walls  built  of  dry  brick,  laid  in  tempered  clay.  Wood,  bitu- 
minous coal,  and  turf,  may  be  used  as  fuel. 

Two  other  descriptions  of  fuel  may  be  used  in  the  manufac- 
ture of  bricks.  The  first  of  these  is  composed  of  the  cinders 
of  bituminous  coal.  These  are  carefully  sifted,  and  the  finer 
portions  are  mixed  with  the  clay,  replacing  about  an  equal  quan- 
tity of  sand.  The  coarser  parts  are  arranged  in  alternate  strata, 
with  dried  brick,  each  stratum  of  which  is  composed  of  seven  hori- 
zontal courses.  The  advantage  of  this  method  is  not  limited  to 
the  cheap  description  of  fuel,  but  insures  a more  perfect  burning 
of  the  brick,  because  the  ashes  contain  a considerable  quantity 
of  carbonaceous  matter.  The  other  fuel  is  the  fine  dust  of  an- 
thracite coal.  Although  it  cannot  be  applied  as  successfully  as 
the  cinders  of  bituminous  coal,  yet  by  mixing  it  with  the  brick  a 
considerable  quantity  of  fuel  may  be  saved,  and  the  brick  will  be 
more  thoroughly  burnt. 

Tile  is  made  of  the  same  clay  as  brick ; but  the  sand  mixed 
with  the  clay  must  be  finer.  When  used  in  the  interior  of  build- 
ings, it  need  not  be  rendered  impervious  to  water.  When  used 
for  roofing,  it  requires  to  be  glazed  at  least  on  one  side. 

The  glazing  of  pottery  consists  in  covering  it  with  a vitrifia- 
ble  substance,  which  in  the  burning  is  converted  into  a coat  of 
glass.  It  may  be  applied  either  before  burning,  or  after  the 
ware  has  been  once  passed  through  the  fire.  In  this  intermediate 
state  the  ware  is  called  biscuit. 

Tile  is  generally  glazed  while  raw ; the  glaze  is  a mixture  of 
clay,  water,  and  the  oxides  of  lead  and  manganese.  This  mix- 
ture is  applied  to  one  of  the  surfaces  with  a brush.  In  placing 
tile  in  the  kiln,  great  care  must  be  taken  to  prevent  the  surfaces 
from  touching  each  other,  and  to  let  the  diff'erent  layers  touch  at 
as  few  surfaces  as  possible. 

2.  Common  red  and  black  ware  is  made  of  brick  clay  ; the 
glaze  is  also  applied  to  it  while  raw.  The  red  ware  is  glazed 
with  a mixture  of  red  lead  and  white  clay  ; the  black  with  clay, 
red  lead,  and  oxide  of  manganese. 


40 


ALUMINUM. 


3.  Stone  ware  is  made  in  Europe  of  a white  clay  called  pipe- 
clay, and  powdered  flints.  In  this  neighborhood,  there  exist 
many  beds  of  clay  containing  a sufficient  quantity  of  silica. 
Stone  ware  is  glazed  by  throwing  common  salt  into  the  kiln, 
after  the  ware  has  been  brought  to  a white  heat.  This  becomes 
volatile',  and  thus  comes  in  contact  with  every  part  of  the  surface, 
where  a silicate  of  soda  is  formed,  which  fuses. 

To  form  vessels  of  clay,  an  apparatus  called  the  potter’s  wheel 
is  employed.  This,  in  its  original  form,  was  a circular  table  mount- 
ed upon  a vertical  spindle.  Bars  project  from  the  spindle,  within 
reach  of  the  foot  of  the  workman,  who  by  successive  blows  gives 
the  bar  a rotatory  motion.  If  a ball  of  clay  were  laid  on  the  table, 
it  would  spread  out  into  the  form  of  a circular  plate.  But,  if  its 
outward  motion  be  restrained,  it  may  be  made  to  take  the  form  of 
a hollow  vessel.  This  is  effected  by  the  hands  of  the  workman. 

The  first  improvement  of  the  potter’s  wheel  consisted  in 
bending  the  spindle,  so  as  to  form  a crank  ; and  applying  to  the 
crank  a connecting  rod  attached  to  a treddle.  By  applying  the 
foot  to  this  treddle,  the  required  rotatory  motion  is  given  to  the 
spindle.  To  render  the  figure  of  the  vessel  more  perfect,  tools 
made  of  sheet  metal  are  employed.  These  are  cut  to  the  shape 
intended  to  be  given  to  the  outside  of  the  vessel. 

Shallow  vessels  are  made  by  means  of  mo'ulds  of  plaster  of 
Paris.  These  are  set  upon  small  potter’s  wheels  of  the  original 
form.  The  clay  is  rolled  out  into  a thin  sheet,  which  is  applied 
to  the  mould  and  pressed  down  upon  it  by  means  of  a wet  sponge, 
while  the  wheel  revolves  slowly.  To  give  a more  perfect  form  to 
vessels  made  in  either  way,  they  are,  after  being  partially  dried, 
applied  again  to  the  potter’s  wheel,  upon  which  they  are  caused 
to  revolve,  while  a cutter  of  sheet  metal  is  applied  to  the  sur- 
face. A more  perfect  form  may  be  given  by  the  use  of  the  turn- 
er’s lathe. 

When  the  required  figure  is  irregular,  it  is  made  by  applying 
thin  sheets  of  clay  to  moulds  of  plaster,  and  uniting  the  several 
pieces  by  a liquid  mixture  of  clay  and  of  water  (slip).  In  this 
way  the  spouts  of  vessels  are  made  and  attached.  Rods  may  be 
made  by  forcing  clay  through  a hole  in  the  bottom  of  an  iron 


ALUMINUM. 


41 


box.  These  rods  may  be  cut  and  bent,  and  of  them  the  handles 
of  vessels  are  formed.  By  placing  a mandril  in  the  box,  hollow 
pipes  may  be  made. 

The  kiln  used  in  burning  the  cheaper  kinds  of  ware  is  an 
oven,  whose  floor  is  inclined.  A fire  is  made  at  the  lower  end, 
and  the  smoke  and  heated  air  aj^e  directed  through  the  kiln  by 
an  opening  in  the  opposite  extremity  and  smaller  ones  in  the 
vault. 

The  kilns  used  for  the  better  kinds  of  pottery  are  cylindrical 
chambers,  covered  by  a dome.  Around  the  base  of  the  chamber 
a number  of  fire-places  are  arranged  at  equal  distances,  each 
having  an  opening  communicating  with  the  chamber.  Below 
each  of  these  openings  a passage  is  formed  in  the  floor  of  the 
kiln,  leading  to  an  opening  in  the  centre  of  the  floor,  and  above 
each  of  the  openings  is  a vertical  flue.  To  provide  for  the  escape 
of  the  smoke,  a large  opening  is  made  in  the  middle  of  the  door, 
and  small  openings  around  its  circumference.  To  create  a 
draught,  a hollow  cone  is  built  upon  the  walls  which  inclose  the 
kiln.  Formerly,  a much  larger  conoidal  chamber  was  built 
over  and  around  the  kiln.  In  the  French  potteries  several  kilns 
have  been  built  over  each  other ; by  this  means  all  loss  of  heat  is 
prevented,  and  by  placing  furnaces  on  floors  corresponding  to  the 
divisions  of  the  kilns,  the  lower  portions  may  be  permitted  to 
cool,  while  heat  is  applied  to  those  above. 

4.  Delft  ware  may  be  made  of  any  kind  of  clay,  and  is  usually 
made  of  that  which  takes  a red  color.  The  surface  is  rendered 
white  and  opaque  by  glazing  it,  when  in  the  state  of  biscuit,  with 
an  opaque  white  glass.  This  kind  of  ware  was  known  to  the 
Bomans,  and  was  made  in  the  middle  ages  at  Faenza  in  Italy. 
It  was  long  manufactured  at  the  place  whence  it  obtains  its 
name,  but  has  been  superseded  for  about  a century  by  Queen’s 
ware. 

5.  Queen’s  ware  is  made  of  a mixture  of  pipe-clay  and  pow- 
dered flints.  They  are  ground  together  with  such  an  excess  of 
water  that  the  mixture  may  be  passed  through  a bolting-cloth. 
The  excess  of  water  is  removed  by  boiling  in  a pan  formed  of 
large  glazed  tiles.  Some  difficulty  is  experienced  in  removing 


42 


ALUMINUM. 


the  cavities  formed  by  the  bubbles  of  vapor.  The  ware  is  fash- 
ioned on  the  potter’s  wheel,  and  afterwards  turned  on  a lathe. 
Of  late  the  potter’s  wheel  used  in  this  manufacture  has  been 
driven  by  steam,  which  it  was  once  considered  impossible  to 
substitute  in  this  case  for  human  intelligence.  The  dried  ware 
is  converted  into  biscuit  in  a kiln  of  the  improved  form. 

The  biscuit  is  coated  with  the  materials  of  the  glaze,  by  being 
dipped  in  a vessel,  in  which  they  are  kept  in  a state  of  suspen- 
sion in  water  by  agitation.  The  materials  of  the  glaze  are  car- 
bonate of  lead  and  powdered  flints. 

Great  care  must  be  taken  to  apply  the  heat  gradually  to  the 
raw  ware,  and  the  heat  is  at  last  carried  to  whiteness.  This  op- 
eration always  requires  several  days,  and  when  the  pieces  are 
large,  may  occupy  a week  or  two.  No  such  precaution  is  ne- 
cessary in  glazing,  and  the  vitrification  may  be  completed  in  a 
few  hours. 

Bituminous  coal  is  the  only  fuel  that  has  been  employed  in 
making  Queen’s  ware.  To  prevent  the  ware  from  being  dis- 
colored by  the  smoke  of  this  fuel,  it  is  inclosed,  both  in  burning 
the  biscuit  and  in  glazing,  in  vessels  called  saggers.  These  are 
set  one  upon  the  other,  and  their  joints  are  luted  with  tempered 
clay.  The  saggers  used  in  glazing  must  be  themselves  glazed, 
or  dipped  in  the  materials  of  the  glaze.  To  prevent  the  several 
pieces  from  adhering  while  the  glaze  is  vitrified,  they  are  sepa- 
rated from  each  other  by  crowsfeet,  made  each  of  three  strips  of 
tempered  clay. 

Queen’s  ware  is  often  embellished  with  colored  figures.  These 
are  composed  of  enamels,  and  are  sometimes  applied  to  the  sur- 
face of  the  glaze,  at  other  times  to  that  of  the  biscuit.  The 
colors  are  ground  with  gum  or  glue,  and  may  be  laid  on  with  a 
hair-pencil.  This  method  is  too  costly  for  any  but  rude  figures. 
More  perfect  figures  are  applied  by  'printing.  In  printing,  en- 
gravings on  copper  are  employed.  By  means  of  them  impres- 
sions are  taken  in  the  engraver’s  press  on  well  sized  paper.  The 
paper,  after  being  moistened,  is  pressed  upon  the  surface  of  the 
ware.  A great  part  of  the  paper  is  removed  by  rubbing  it  with 
the  finger,  and  the  remainder  is  burnt  away,  when  the  ware  is 


ALUMINUM. 


43 


exposed  in  a kiln  to  a heat  sufficient  to  vitrify  the  enamel  color. 
The  favorite  color  is  blue,  obtained  by  means  of  the  oxide  of  co- 
balt ; and  the  blue  printed  Queen’s  ware  is  known  among  us  as 
Liverpool  China. 

6.  Porcelain  is  distinguished  from  other  ware  by  being  trans- 
lucent. It  is  of  so  ancient  a date  in  China,  that  vessels  with 
Chinese  characters  have  been  found  in  the  catacombs  of  Egypt 
of  a date  certainly  earlier  than  the  Persian  conquest.  It  is 
made  of  even  better  quality  in  Japan,  and  is  also  manufactured 
in  Persia. 

When  porcelain  was  first  brought  from  China  into  Western 
Europe,  it  was  inferred  that  it  must  be  composed  of  two  sub- 
stances, one  of  the  nature  of  clay  and  infusible,  the  other  fusible. 
To  imitate  it,  pipe-clay  was  mixed  with  powdered  glass.  It  was, 
however,  found  necessary  to  add  so  much  of  the  latter  material, 
that  the  mixture  lost  its  plasticity,  and  could  not  be  fashioned  on 
the  potter’s  wheel.  This  defect  was  partially  remedied  by  using 
a marly  clay,  and  tempering  the  mixture  with  water  rendered 
viscid  by  soap.  The  latter  was  the  composition  of  the  ancient 
porcelain  of  Sevres.  The  same  composition  is  also  still  employed 
in  some  of  the  French  manufactories,  and  in  the  ware  styled  Iron 
Stone  by  the  English.  The  glaze  was  powdered  glass.  Porce- 
lain made  of  these  materials  is  brittle,  both  when  struck  and 
when  suddenly  heated  or  cooled,  and  it  is  easily  fused. 

The  clay  used  by  the  Chinese  was  brought  to  Europe ; but 
although  a similar  material  was  soon  found,  the  discovery  was  of 
no  value,  for  want  of  a knowledge  of  the  other  materials.  Fi- 
nally, specimens  of  the  other  material  used  in  the  body  of  the 
Chinese  ware  was  sent  to  Europe,  and  found  to  be  the  abundant 
mineral,  felspar. 

The  best  French  porcelain  is  now  made  of  China  clay,  mixed 
with  powdered  felspar.  After  being  burnt  into  biscuit,  it  is 
coated  with  a glaze  of  felspar,  by  dipping  in  a vessel  containing 
water  in  which  that  material  is  suspended  by  means  of  gum.  In 
the  Dresden  China,  besides  these  two  materials,  sulphate  of  baryta 
is  mixed  with  the  body  of  the  ware.  The  glaze  is  the  same  as 
that  of  the  French. 


44 


ALUMINUM. 


At  Worcester,  in  England,  no  less  than  seven  different  earthy 
minerals  are  used  in  the  body  of  the  ware.  The  material  em- 
ployed by  the  Chinese  in  their  glaze,  has  been  recently  ascer- 
tained. It  is  a transparent  and  colorless  sulphate  of  lime. 

At  Sevres  and  Dresden,  it  requires  a higher  and  longer  con- 
tinued heat  to  vitrify  the  glaze  than  to  bake  the  biscuit. 

7.  The  body  of  Wedgewood  ware  is  composed  of  clay,  powder- 
ed flints,  and  sulphate  of  baryta.  The  materials  of  the  glaze  do 
not  appear  to  be  known, 

8.  The  Hessian  crucibles  are  made  of  a refractory  clay,  mixed 
with  a pure  quartzy  sand. 

In  Wedgewood  crucibles  the  raw  clay  is  mixed  with  clay  that 
has  been  previously  burnt,  and  reduced  to  powder.  In  black- 
lead  crucibles  the  clay  is  mixed  with  plumbago.  In  general  the 
quantity  of  raw  clay  is  no  more  than  will  cause  the  material  to 
adhere.  Crucibles,  therefore,  are  usually  made  in  moulds  com- 
posed of  a hollow  vessel  of  brass  and  a solid  piece  of  the  same 
material  attached  to  a rod,  and  applied  to  ram  the  tempered  clay 
into  the  space  between  it  and  the  vessel. 


VII 


CALCIUM. 


1.  MINERALOGY  OF  LIME. 

Species  1. — Carbonate  of  Lime. 

The  carbonate  of  lime  is  a very  abundant  natural  product. 
It  occurs  in  many  different  forms,  of  which  the  following  are  the 
most  important. 

1.  Crystallized,  the  primitive  form  being  a rhomb,  and  the 
secondary  forms  more  numerous  and  varied,  than  those  of  any 
other  mineral.  When  transparent  it  is  doubly  refracting,  and 
when  colorless  as  well  as  transparent,  it  is  called  Iceland  spar. 

2.  Granular.  When  the  grains  are  fine,  it  is  said  to  be  sanha- 
roid,  and  this  when  of  a pure  white  color  is  called,  from  its  use, 
statuary  marble.  Of  this,  the  only  localities  that  have  been  much 
quarried  are  those  of  Paros,  and  Carrara.  When  of  coarser 
grain  it  is  used  as  a building  stone,  being  a material  of  great 
beauty,  and  one  of  the  few’  that  withstand  the  severity  of  our 
climate.  Of  this  variety  the  Parthenon  and  several  other  build- 
ings at  Athens  are  specimens, 

3.  Stalactite  hangs  from  the  roof  of  caverns.  Stalagmite 
collects  on  the  floors  of  caverns,  and  travertine  forms  in  stagnant 
waters.  All  of  them  are  deposited  in  proportion  to  the  quantity 
of  the  excess  of  acid  that  escapes.'  Stalactite  when  cut  across 
exhibits  the  several  layers  of  its  deposition,  distinguishable  by  dif- 
ferent shades  of  color,  and  takes  a high  polish.  It  is  also,  often 


46 


CALCIUM. 


translucent,  and  when  it  possesses  both  properties  is  used  in  the 
manufacture  of  ornamental  slabs  and  vases.  It  is  included  by 
the  Italians,  under  the  name  of  labastro^  or  alabaster.  When  a 
similar  deposit  takes  place  in  a bed  of  sand,  calcareous  sandstone 
is  formed,  and  when  the  deposit  takes  place  in  beds  of  pebbles, 
the  conglomerate  is  called  breccia  or  pudding-stone.  When  the 
pebbles  take  as  high  a polish  as  the  carbonate  of  lime,  the  breccia 
is  a fine  marble.  Of  this  a fine  description  has  been  used  in  the 
pillars  of  the  Houses  of  Congress,  at  Washington. 

4.  Compact.  When  this  is  free  from  other  earthy  matter,  it 
takes  a high  polish,  and  comprises  the  greater  part  of  the  mar- 
bles. The  difference  among  them  arises,  in  part,  from  colors 
given  by  metallic  oxides.  These  are  variegated  by  veins  of  white, 
or  patches  of  other  colors.  Organic  remains  also  occur  in  them, 
as  petrifactions  of  a difterent  hue  from  the  general  mass.  When 
the  marble  is  black,  the  coloring  matter  is  carbon.  When  mixed 
with  other  matter,  the  compact  carbonate  is  of  little  use  except 
in  the  manufacture  of  lime,  or  as  a building  stone.  When  mixed 
with  argillaceous  matter  it  is  the  basis  of  an  hydraulic  cement. 

5.  Oolite,  occurring  in  spherical  concretions. 

6.  Chalk. 

Species  2. — Arragonite. 

This  is  also  a carbonate  of  lime,  differing  from  the  preceding 
species  in  its  crystalline  form,  and  in  being  harder.  It  is  com- 
paratively rare,  occurring  in  crystals,  either  detached  or  in  groups 
on  the  surface  of  ores  of  iron.  It  also  forms  a translucent  stalac- 
tite of  even  greater  beauty  than  the  former,  of  which  the  finest 
specimen  extant  is  the  sarcophagus  of  an  Egyptian  king,  now  at 
Cambridge,  England. 

Species  3. — Sulphate  of  Lime. 

A hydrate  of  that  salt,  which  occurs  in  crystals  called  selenite, 
in  white  granular  masses,  which  are  translucent,  and  to  which 
the  name  of  alabaster  is  usually  restricted  in  our  language ; of 
dark  colors,  granular,  earthy,  and  compact,  in  which  forms  it  is 
called  gypsum,  or  from  its  use,  plaster  of  Paris. 


V 


CALCIUM. 


47 


Species  4. — Phosphate  of  Lime, 

This  has  hitherto  been  a very  rare  mineral,  but  has  recently 
been  found  in  tolerable  abundance  at  two  localities,  in  the  Atlantic 
States. 

Species  5. — Magnesian  Carbonate  of  Lime. 

A compound  of  the  carbonates  of  two'  earths.  When  found 
in  crystals  it  is  called  bitter  spar ; when  granular,  dolomite  ; and 
when  compact,  magnesian  limestone.  The  granular  variety  oc- 
curs in  great  abundance  mixed  with  granular  carbonate  of  lime  in 
the  white  marbles  of  Westchester  Co.  When  of  sufficiently 
firm  structure,  these  are  not  only  the  most  beautiful,  but  also  the 
most  durable  of  our  building  stones.  The  magnesian  limestone 
of  England  has  by  the  experience  of  centuries  been  found  to  be 
the  most  lasting  material  employed  in  that  country. 


2.  MANUFACTURE  OF  LIME. 

Lime  may  be  made  of  any  mineral  of  which  its  carbonate 
forms  the  principal  part.  It  is  prepared  in  kilns  of  two  kinds, 
the  common  and  perpetual. 

The  common  kiln  is  a pyramidal  building,  the  chamber  within 
which  is  sometimes  egg-shaped,  but  more  frequently  conical.  On 
one  side  of  the  chamber  is  a low  door.  The  limestone  is  broken 
into  pieces,  none  of  which  should  exceed  six  inches  in  length.  With 
the  largest  of  these,  an  irregular  vault  is  built  over  the  door,  and 
upon  this  vault  the  rest  of  the  lime  is  thrown  and  heaped  upon 
the  upper  opening.  The  space  beneath  the  vault  serves  as  a fur- 
nace, into  which  the  fuel  is  admitted  through  the  door.  Any 
fuel  which  burns  with  fiame  may  be  employed,  and  when  coal  or 
turf  is  used,  an  iron  grate  must  be  placed  beneath  the  vault. 
The  only  precaution  necessary  is,  that  the  heat  should  not  be 
raised  too  suddenly.  When  the  whole  of  the  carbonic  acid  is 
driven  oft’,  the  fire  is  extinguished  and  the  lime  removed. 

Perpetual  kilns  will  make  a given  quantity  of  lime  with  much 


48 


CALCIUM. 


less  fuel ; they  are  of  two  kinds,  the  one  adapted  to  bituminous 
coal,  the  other  to  anthracite.  When  bituminous  coal  is  to  be  used, 
the  body  of  the  kiln  is’  a chimney  20  or  30  feet  in  height.  Ad- 
joining to  the  base,  a furnace  is  built  having  grate  bars,  and  an 
ash-pit.  From  the  furnace  there  is  an  opening  into  the  kiln 
above  the  fuel,  and  the  furnace  is  covered  with  an  iron  door. 
Another  opening  is  made  between  the  ash-pit  and  the  kiln,  and 
the  ash-pit  is  also  furnished  with  a door.  In  lighting  the  fire, 
the  ash-pit  is  left  open  and  the  upper  door  is  closed,  but  as  soon 
as  the  fuel  is  ignited  the  ash-pit  is  closed,  and  the  upper  door 
opened.  As  fast  as  the  lime  is  finished,  it  is  raked  out  through 
an  opening  at  the  base  of  the  kiln,  and  the  space  thus  left  filled 
by  throwing  limestone  in  at  the  top.  For  anthracite  coal,  the 
kiln  has  the  form  of  the  common  kilns,  but  is  of  much  greater 
height.  Instead  of  the  door  it  has  a small  opening  near  the  base. 
To  set  it  in  action,  wood  is  thrown  in  and  covered  with  coal. 
Upon  the  coal  is  thrown  a layer  of  limestone ; this  is  covered  with 
a layer  of  coal,  and  thus  alternately  until  the  kiln  is  filled.  The 
lime  when  finished  is  raked  out  from  beneath,  and  fresh  layers  of 
limestone  and  fuel  are  thrown  in  above. 

3.  MORTAK. 

When  hydrate  of  lime  is  mixed  with  water  to  the  consistence 
of  paste,  and  exposed  to  the  air,  the  lime  which  is  in  solution 
receives  carbonic  acid  from  the  atmosphere  and  is  precipitated. 
The  water  dissolves  more  lime  which  in  its  turn  is  precipitated, 
and  thus  the  operation  will  go  on  until  the  whole  of  the  lime  be- 
comes carbonate,  or  until  all  the  water  has  evaporated.  In  this 
way  an  aggregate  of  carbonate  of  lime  is  attained  of  about  the 
hardness  of  chalk.  If  silica  be  present,  the  carbonate  of  lime -will 
be  precipitated  upon  it,  and  the  aggregate  will  be  much  firmer 
than  in  the  former  case.  After  a considerable  time,  the  lime  ap- 
pears to  be  converted  into  a silicate,  but  this  may  not  take  place 
completely  until  after  the  lapse  of  centuries.  We  therefore  find 
in  old  buildings,  mortar  not  only  harder  than  limestone,  but  ca- 
pable of  striking  fire  with  steel. 


CALCIUM. 


49 


To  make  mortar  of  lime  which  slakes  readily,  sand  is  piled 
in  such  a manner  as  to  form  a shallow  hasin.  In  the  basin  the 
lime  is  laid  and  water  is  thrown  upon  it.  As  the  lime  slakes, 
water  is  added  and  the  lime  agitated  until  the  mixture  becomes 
nearly  liquid.  In  this  state  it  is  incorporated  by  degrees  with 
the  sand  until  the  whole  becomes  uniformly  mixed  with  five 
times  its  bulk. 

To  incorporate  so  large  a quantity  of  sand,  requires  much 
labor ; but  the  greater  the  quantity  that  can  be  added,  the  better 
will  be  the  mortar,  up  to  the  limit  of  plasticity. 

When  limestone  contains  carbonate  of  magnesia,  the  lim  ^ 
slakes  slowly  and  cannot  be  treated  in  this  manner.  In  ordcx' 
to  make  a good  mortar  of  this  description  of  lime,  a cavity  is 
formed  in  the  ground,  in  which  the  lime  is  placed  with  a proper 
quantity  of  water.  Upon  these  the  proper  quantity  of  sand  is 
heaped,  and  the  whole  is  left  at  rest  until  the  lime  is  completely 
reduced  to  powder.  When  the  limestone  contains  silicate  of 
alumina,  the  lime  will  not  slake ; it  may  however  be  reduced 
to  powder  by  mechanical  means.  The  mortar  made  from  it  has 
hydraulic  properties,  or,  even  when  it  has  not,  will  set  more 
rapidly  than  mortar  made  from  a purer  lime. 

4.  HYDRAULIC  CEMENT. 

The  material  first  used  in  the  preparation  of  an  hydrsLulie- 
cement  was  puzzolana.  This  substance  was  used  by  the  Ro- 
mans. To  prepare  the  cement,  puzzolana,  which  has  the  ap- 
pearance of  ashes,  is  mixed,  as  in  common  mortar,,  with  pure 
slaked  lime.  The  attraction  of  the  materials  is  so  powerful, 
that  when  prepared  in  small  quantities,  the  cement  will  set  in  a 
few  minutes.  It  therefore  will  not  only  resist  water,  but  will  set 
under  water.  By  means  of  it,  walls  may  be  built  at  considerable 
depths.  The  space  intended  to  be  occupied  by  the  wall,  is  in- 
closed by  a wooden  partition.  The  cement  is  mixed  with  an 
equal  bulk  of  angular  fragments  of  stone,  and  is  permitted  to  lie 
in  a heap  until  it  sets  at  the  surface.  It  is  then  agitated  until 
it  resumes  its  former  consistence,  without  adding  water.  The 
4 


50 


CAl.CiUM. 


mixture  is  then  plunged  to  the  bottom  of  the  space  by  means  of 
a cubical  box  whose  bottom  is  hung  on  hinges.  When  a uni- 
form bed  has  been  thus  spread,  angular  pieces  of  stone,  about  six 
inches  in  length,  are  thrown  upon  it.  Upon  these  is  plunged 
another  layer  of  the  mixture.  When  the  water  becomes  too  shal- 
low for  the  use  of  the  machine,  the  mixture  is  thrown  in  from 
baskets,  and  the  operation  is  continued  until  the  surface  of  the 
water  is  reached,  from  which  level  the  wall  may  be  carried  up- 
wards in  the  usual  manner ; but  so  long  as  the  stones  are  within 
reach  of  water,  the  joints  must  be  filled  with  the  same  cement. 

In  the  Low  Countries,  an  hydraulic  cement  was  prepared 
from  a stone  found  on  the  banks  of  the  Rhine.  This  is  a trapp 
rock.  It  is  prepared  by  heatiug  to  redness,  and  grinding  to 
powder.  When  mixed  with  pure  lime,  it  does  not  set  under 
water  ; but  when  mixed  with  hydraulic  lime,  it  will.  This  sub- 
stance is  called  Trass.  In  Holland  an  artificial  trass  is  prepared 
from  the  mud  taken  from  the  bottom  of  the  canals.  This  is 
moulded  and  burnt,  like  brick,  and  is  then  reduced  to  powder. 
Roth  descriptions  of  trass  must  be  kept  in  tight  casks,  for  they 
a ttract  moisture  rapidly  from  air. 

Hydraulic  cement  may  also  be  prepared  from  the  limestones 
containing  silicate  of  alumina.  These  possess  hydraulic  proper- 
ties in  very  different  degrees  ; when  in  the  highest,  they  must  be 
mixed  with  pure  sand  ; when  in  moderate  degrees,  with  trass  or 
other  silicate  of  alumina  possessing  moderate  hydraulic  proper- 
ties. Puzzolana  is  a pure  silicate  of  alumina.  Trass  contains 
iron  ; if,  in  its  preparation,  the  iron  is  converted  into  peroxide, 
the  properties  of  trass  are  impaired.  The  artificial  trass  owes  its 
good  properties  to  the  presence  of  organic  matter  in  the  mud,  by 
which  the  iron  is  prevented  from  becoming  a peroxide.  The 
brick  is  also  burnt  in  close  kilns.  The  most  powerful  hydraulic 
lime  is  prepared  from  a substance  called  septaria,  found  in  the 
London  clay.  The  prepared  article  is  called  Roman  cement. 
An  inferior  cement  is  prepared  from  poor  calcareous  ores  of  iron. 
When  the  Roman  cement  is  to  be  exposed  to  the  air,  it  ought  to 
be  mixed  with  a large  quantity  of  sand. 

An  artificial  cement  was  formerly  prepared  in  this  city  by  a 
mixture  of  pure  quicklime,  powdered  brick,  and  forge  scales. 


CALCIUM. 


51 


An  artificial  cement  may  Ibe  prepared  wherever  lime  and  clay 
can  be  obtained,  by  mixing  the  claywith  carbonate  of  lime  in  powder, 
forming  the  mixture  into  brick,  and  burning  it  at  a temperature 
less  than  that  at  which  the  mixture  fuses.  If  the  clay  have  a 
red  color  it  ought  to  be  mixed  with  organic  matter,  and  the 
brick  should,  in  all  cases,  be  burnt  in  a close  kiln.  When  chalk 
or  tufa  can  be  obtained,  it  is  mixed  with  the  clay,  but  when  the 
limestone  is  hard  it  is  made_  into  lime  and  exposed  to  the  air  un- 
til it  falls  to  powder.  It  is  then  said  to  be  air  slaked,  and  is 
a carbonate. 


5.  USE  OF  LIME  IN  AGKICULTUKE. 

Lime  is  of  great  value  as  a manure.  Its  uses  in  agriculture 
may  be  in  part  explained  on  the  following  principles : 

1.  Soils  may  contain  so  much  clay  that  water  will  not  sink 
into  them,  and  may  in  dry  weather  become  so  stiff  that  they  can- 
not be  tilled  ; a mixture  of  lime  will  diminish  both  of  the  defects. 

2.  Sandy  soils  permit  water  to  pass  through  them ; a mixture 
of  lime  will  remedy  this  defect. 

3.  Some  soils  contain  an  acid,  which  may  be  neutralized  by 
lime. 

In  the  first  two  instances,  the  lime  ought  to  be  in  a caustic 
state ; in  the  third,  it  may  be  a carbonate, 

4.  Soils  often  contain  organic  matter  that  will  not  decompose. 
The  decomposition  may  be  effected  by  the  application  of  quick- 
lime. 

5.  All  the  seeds  used  in  making  bread,  contain  the  sulphate 
and  phosphate  of  lime,  and  will  not  grow  upon  a soil  that  does 
not  contain  that  earth.  Soils  on  which  wheat  is  grown,  however 
rich  in  other  respects,  may  cease  to  bear  it  unless  lime  be  added 
from  time  to  time.  The  lime  used  in  this  case  ought  to  be  in 
the  state  of  carbonate,  for  quicklime  will  destroy  the  organic 
matter  in  the  soil. 

6.  All  loose  earths  have  the  power  of  absorbing  the  gases 
which  are  generated  by  putrefaction.  But  carbonate  of  lime  pos- 


52 


CALCIUM. 


sesses  this  quality  in  the  highest  degree.  These  gases  are  the 
most  important  part  of  the  food  of  plants,  and  are  not  only  found 
in  greater  abundance,  but  are  retained  for  a longer  time  in  cal- 
careous soils., 

These  gases  are  chiefly  the  carburets  of  hydrogen  and  am- 
monia, the  latter  being  derived  from  animal  manures. 

The  proper  mode  of  applying  putrescent  manures,  would  be 
to  bury  them  as  deeply  as  possible ; and  of  applying  the  carbonate 
of  lime,  to  lay  it  upon  the  surface. 

The  cases  in  which  quicklime  can  be  applied,  have  been  stated. 
In  all  other  cases  the  lime  ought  to  be  in  the  form  of  carbonate. 
This  is  sometimes  found  mixed  with  clay,  under  the  name  of 
marie,  which  is  a valuable  manure.  When  chalk  can  be  procured 
it  will  fall  to  pieces  when  exposed  to  frost,  and  may  also  be  em- 
ployed without  preparation.  Shells  not  only  contain  carbonate  of 
lime,  but  also  organic  matter.  The  best  mode  of  preparing  these 
is  to  crush  them.  When  limestones  are  to  be  used,  the  cheapest 
mode  of  reducing  them  to  powder  is  by  burning  and  slaking. 
But  the  powder  ought  to  be  exposed  to  the  air,  until  it  is  satura- 
ted with  carbonic  acid,  before  it  is  spread  over  the  soil. 

When  lime  contains  magnesia  it  must  be  used  with  great  cau- 
tion, and  it  will  be  rarely  safe  to  apply  more  than  20  or  30  bushels 
per  acre,  and  this  at  intervals  of  several  years.  In  Great  Britain 
as  much  as  600  bushels  of  slaked  lime  have  been  applied  to  stiff 
clay,  and  from  200  to  300  to  sand.  These  quantities  should  not 
be  applied  at  less  intervals  than  20  years. 

The  most  economic  mode  of  using  lime  is  practised  in  France. 
Here  quicklime  is  mixed  in  regular  layers  with  sods.  The  mixture 
is  stirred  several  times  and  permitted  to  remain  where  placed,  until 
all  the  lime  is  carbonated.  Seven  bushels  per  acre  is  sufficient, 
but  it  ought  to  be  repeated  with  every  grain  crop. 

Sulphate  of  lime  is  also  used  in  agriculture,  under  the  name 
of  plaster.  The  hydrated  sulphate  is  prepared  by  being  ground  to 
powder,  and  a single  bushel  per  acre  is  sufficient,  while  a quan- 
tity as  great  as  5 or  6 would  be  injurious.  There  are  certain 
plants,  the  ashes  of 'which  are  chiefly  composed  of  sulphate  of 
lime  > those  of  red  clover  contain  little  else.  The  latter  plant. 


CALCIUM. 


53 


will  not  grow  in  any  soil  that  does  not  contain  this  sulphate. 
It  is  therefore  applied  first  to  obtain  a large  crop  of  clover, 
which  draws  the  rest  of  its  nutriment  chiefiy  from  the  atmos- 
phere, Permanent  fertility  may  be  obtained  by  ploughing  in 
such  crops  of  clover ; but  where,  at  least,  one  crop  of  clover  is 
not  ploughed  in,  the  use  of  plaster  injures  instead  of  improving 
the  soil.  Sulphate  of  lime  would  produce  no  effect  in  soils  which 
already  contain  it,  or  in  soils  containing  oxalic  acid.  When  the 
latter  is  present  it  may  be  neutralized  by  the  application  of  the 
carbonate  of  lime,  and  soils  on  which  plaster  has  ceased  to  act 
may  thus  be  rendered  sensible  to  its  action. 

The  phosphate  of  lime  is  of  even  more  value  as  a manure 
than  the  sulphate,  for,  although  larger  quantities  may  be  neces- 
sary to  produce  an  effect,  it  is  a substitute  for  other  manures  of 
animal  origin.  The  phosphate  of  lime  has  been  most  usually  ap- 
plied in  the  form  of  pulverized  bones,  but  the  mineral  sources 
that  have  been  heretofore  spoken  of  will,  probably,  hereafter  be 
resorted  to. 

The  phosphate  of  lime  as  found,  either  mineral  or  in  bones,  is 
insoluble.  It  may  be  converted  into  a soluble  salt  by  the  addi- 
tion of  sulphuric  acid.  In  this  state  it  acts  much  more  rapidly, 
and  therefore  may  be  used  in  less  quantities,  although  it  will  re- 
quire to  be  more  frequently  repeated. 


VIII. 


SALTS  OF  COMMERCE. 


' 1.  COMMON  SALT. 

The  sources  of  common  salt  are  the  water  of  the  ocean,  brine- 
springs,  and  geological  formations,  where  it  exists  in  a solid  form 
called  Rock  Salt.  In  one  particular  case,  viz.  near  Cracow  in 
Poland,  rock  salt  exists  in  such  plenty  as  to  require  no  other  pre- 
paration than  crushing.  In  order  to  prepare  it  for  carriage,  it  is 
cut  into  blocks  of  the  shape  of  a barrel,  and  these  are  surrounded 
by  staves  and  hoops.  In  most  other  cases  the  rock  salt  is  mixed 
with  insoluble  earthy  matter  as  well  as  rendered  impure  by  other 
soluble  salts.  It  therefore  becomes  necessary  to  dissolve  it. 
The  insoluble  matters  which  subside,  may  be  separated  by  decant- 
ing the  solution.  At  the  salt  mines  in  Cheshire  in  England, 
brine  springs  issue  from  the  salt  formations,  and  the  rock  salt  is 
dissolved  in  the  water  of  these.  The  rock  salt  is  also  carried  to 
Liverpool,  where  it  is  dissolved  in  sea  water.  Erom  such  solu- 
tions, as  well  as  from  the  waters  of  the  ocean  and  brine  springs, 
salt  is  obtained  by  evaporation  and  crystallization. 

The  preparation  of  the  salt  in  all  three  cases  rests  upon  the 
same  general  principles.  The  substances  contained  in  these 
waters  besides  common  salt  are,  1 st,  the  carbonates  of  iron  and 
lime,  held  in  solution  by  excess  of  acid ; 2d,  sulphate  of  lime ; 
3d,  sulphate  of  soda;  and  4th,  chlorides  of  calcium  and  magnesia, 
which  are  usually  known  under  the  name  of  earthy  muriates. 


SALTS  OF  COMMERCE. 


55 


The  carbonates  of  iron  and  lime  may  be  precipitated  by  a mod  - 
erate  heat,  or  by  merely  permitting  the  liquid  to  remain  at  rest 
in  contact  with  the  air.  They  may  then  be  separated  by  decant- 
ing. Of  the  remaining  salts,  the  sulphate  of  lime  alone  is  less 
soluble  than  common  salt ; but  when  the  sulphate  of  soda  is  also 
present  a double  salt'  is  formed,  which,  although  more  soluble 
than  sulphate  of  lime,  is  much  less  soluble  than  common  salt. 
When  therefore  a saline  water  is  evaporated,  either  artificially  or 
spontaneously,  the  double  sulphate  of  lime  and  soda  will  be  de- 
posited early  in  the  process,  and  collect  in  a hard  crust  upon  the 
vessels  or  natural  basins  which  contain  the  liquid.  Common 
salt  will  next  be  deposited  in  crystals,  and  these  are  loose.  It 
may  therefore  readily  be  separated  from  the  liquid  even  while 
the  evaporation  is  going  on.  When  the  crystals  are  large,  this 
may  be  performed  by  rakes.  The  earthy  muriates  have  a bitter 
taste.  The  evaporation,  therefore,  ought  not  to  be  continued  be- 
yond the  point  at  which  this  taste  begins  to  be  sensible  in  the 
salt.  The  remaining  liquid  which  goes  under  the  name  of  bit- 
tern, is  thrown  away. 

In  the  manufacture  of  salt  from  sea  water,  the  evaporation 
may  be  performed  either  by  exposure  to  the  air,  or  by  artificial 
heat,  and  even  in  the  latter  case  the  process  may  be  made  to  as- 
sume the  character  of  a spontaneous  evaporation. 

There  are  certain  places  in  warm  climates  where  the  sea 
water  is  admitted  at  spring-tides  into  shallow  natural  basins.  In 
these,  salt  is  often  crystallized  and  may  be  raked  from  them. 
Such  natural  basins  exist  at  Turk’s  Island,  and  at  Key  West. 
In  other  places  artificial  basins  are  formed,  called  fialt-pans.  In 
order  to  form  one  of  these,  a portion  of  salt  meadow  is  chosen 
and  inclosed  by  dykes.  Within  the  outer  dyke  a sort  of  laby- 
rinth is  formed,  in  which  the  water  is  first  concentrated  and  the 
salt  finally  crystallized.  The  first  part  of  this  labyrinth  is  a large 
basin  or  reservoir  which  communicates  with  the  tide  by  gates. 
The  water  is  led  from  this  through  a canal  which  follows  the 
course  of  the  outer  dyke,  thus  forming  three  sides  of  a square,  and 
has  a branch  parallel  to  the  reservoir,  which  nearly  forms  the  fourth 
side,  and  conveys  the  water  almost  back  to  the  place  where  the 


56 


SALTS  OF  COMMEECE. 


canal  first  issued  from  the  reservoir.  Within  the  square  thus 
formed  are  two  sets  of  rectangular  basins.  In  the  first  of  these 
the  water  circulates,  passing  through  them  diagonally.  From 
these  the  water  is  admitted  into  the  basins  of  the  second  set,  in 
each  of  which  a portion  of  the  water  is  shut  up  until  the  crystalli- 
zation is  completed,  and  after  the  salt  begins  to  form  in  them  it 
is  raked  out.  Salt  is  obtained  in  this  way  in  large  cubic  crystals, 
and  is  called  Bay  Salt.  In  this  form  it  is  found  to  be  better 
suited  for  preserving  meat  than  when  fine.  Large  crystals  may 
also  be  obtained  by  artificial  heat,  by  taking  care  not  to  permit 
the  liquid  to  boil.  When  the  boiling  is  rapid,  the  crystals  are 
so  small  as  to  be  separately  invisible,  and  the  product  is  fine  or 
table  salt. 

If  the  artificial  evaporation  be  carried  on,  as  it  frequently  is, 
until  the  whole  of  the  liquid  is  evaporated,  the  earthy  muriates 
will  be  crystallized  with  it  and  give  it  a bitter  taste.  These 
earthy  muriates  are  deliquescent  and  very  soluble.  Hence  they 
are  sometimes  separated  from  fine  salt,  in  the  following  manner. 
The  salt  is  packed  in  baskets,  which  are  suspended  over  a pan 
in  which  the  artificial  evaporation  is  going  on.  ^ The  steam  which 
.rises  is  condensed  in  the  salt,  and  dissolves  these  deliquescent 
substances  together  with  a portion  of  the  salt.  This  portion 
however  is  comparatively  small,  because  the  water  has  the  boiling 
temperature  and  will  thus  dissolve  much  more  of  the  muriates 
than  when  cold,  although  it  takes  little  more  of  common  salt. 
The  baskets  are  set  by  to  drain,  and  then  dried  by  artificial  heat. 

In  very  cold  climates  the  water  of  the  ocean  has  been  con- 
centrated by  frost.  When  water  containing  salt  freezes,  the  ice 
is  perfectly  fresh,  hence  it  is  only  necessary  to  separate  the  ice 
as  it  forms,  and  the  strength  of  the  brine  will  be  much  increased. 
This  method  is  practised  in  the  eastern  part  of  Siberia.  The 
brine  which  remains  is  evaporated  by  artificial  heat. 

In  the  Dutch  herring  fishery,  the  best  bay  salt  is  employed, 
but  before  this  is  used  it  is  dissolved  in  sea  water,  and  purified 
by  a second  crystallization. 

The  water  of  brine  springs  may  be  evaporated  by  artificial 
heat  in  the  same  manner  as  that  of  the  ocean.  Large  rectangu- 


SALTS  OF  COMMEECE. 


57 


lar  vessels  of  sheet  iron  are  the  best  for  this  purpose,  but  in  this 
State,  and  generally  in  the  U.  S.,  cast-iron  boilers  of  the  form  of 
potash  kettles  are  employed.  In  these,  the  evaporation  is  ofte 
carried  to  dryness,  and  thus  the  salt  is  impure.  It  will  howeve, 
purify  itself  if  permitted  to  drain ; for  the  earthy  muriates  will 
deliquesce,  and  the  solution  thus  formed  will  drain  off.  The 
purification  may  be  performed  more  rapidly  by  adding  a thou- 
sandth part  of  its  weight  of  boiling  water  to  the  salt.  In  order 
to  perform  the  draining  more  effectually  the  salt  should  be  placed 
in  bins,  the  bottom  of  which  is  inclined  and  pierced  with  small 
holes. 

In  this  State  a method  called  Solar  evaporation  has  been 
used  to  obtain  coarse  salt.  Brine  is  poured  into  shallow  wooden 
troughs.  Each  of  these  is  furnished  with  a cover  which  runs 
upon  a railway,  so  that  it  may  be  placed  over  the  trough  when  it 
rains,  and  removed  when  the  weather  is  fine.  The  principal  ob- 
jection to  this  method  is  the  great  extent  of  valuable  ground  re- 
quired for  this  purpose. 

At  some  of  the  salt  springs  in  Europe,  a greater  extent  of 
evaporating  surface  is  obtained  within  a very  small  space.  The 
methods  used  for  this  purpose  are  three ; that  of  hurdles,  that  of 
tables,  and  that  of  ropes.  In  the  method  of  hurdles  a number 
of  bundles  of  the  twigs  of  a thorny  shrub  are  piled  in  a frame 
building.  Over  the  hurdles  is  situated  a trough,  into  which  the 
brine  is  pumped.  This  trough  has  notches  cut  on  its  sides 
through  which  streams  of  the  brine  pass  and  fall  upon  the  twigs. 
The  quantity  of  brine  is  regulated  by  means  of  two  sliding  boards 
in  which  similar  notches  are  formed. 

In  the  method  of  tables,  a number  of  surfaces  of  wood  are 
arranged  one  over  the  other  in  a lofty  building.  Each  table  is 
slightly  inclined,  and  the  alternate  tables  are  inclined  in  opposite 
directions.  Brine  being  admitted  upon  the  upper  table  will 
therefore  flow  slowly  over  the  surface  of  them  all 

In  the  method  of  ropes,  cords  are  stretched  between  two 
troughs,  one  of  which  is  situated  immediately  over  the  other. 
The  upper  trough  being  filled  to  overflowing,  the  brine  will  trickle 
over  the  surface  of  the  ropes.  This  method  has  been  found 


58 


SALTS  OF  COMMEECE. 


especially  advantageous  for  causing  the  crystallization  of  salt  from 
a boiling  and  saturated  solution. 

2.  NITEE. 

The  greater  part  of  the  nitre  of  commerce  is  obtained  from 
soils  in  which  it  is  spontaneously  formed.  It  may  also  be  obtain- 
ed from  artificial  nitre  beds  composed  "of  earth,  and  specially 
prepared  for  the  purpose.  The  soils  in  which  nitre  is  formed 
spontaneously  are  found  wholly  in  warm  countries,  and  Bengal 
at  this  moment  supplies  the  greater  part  of  the  world  with  nitre. 
Nitre  cannot  be  formed  in  a soil  which  does  not  contain  potassa^ 
but  the  other  nitrates  may  be  formed  in  any  soil  which  contains 
their  base.  No  nitrate  will,  however,  be  formed  in  a soil  which 
does  not  contain  animal  matter ; and  it  was  at  one  time  supposed 
that  the  whole  of  the  nitrogen  in  the  nitric  acid  was  derived  from 
the  animal  substance.  It  is  now,  however,  known  that  the  quan- 
tity of  nitre  is  much  greater  than  can  be  thus  accounted  for.  It 
is  therefore  inferred  that  the  animal  matter  acts  only  as  a fer- 
ment, and  that  when  the  process  is  once  commenced,  both  the 
nitrogen  and  oxygen  are  derived  from  the  atmosphere.  The  soil 
of  Bengal  and  Ceylon  contain,  besides  nitre,  the  nitrate  of  lime, 
which  may  be  converted  into  nitre,  and  other  saline  matters 
which  crystallize  with  it  and  render  it  impure.  These  salts  are 
separated  from  the  earth  by  lixiviation.  If  wood  ashes  be  pre- 
viously mixed  with  the  earth,  the  nitrate  of  lime  will  be  converted 
into  nitre.  The  same  change  may  also  be  effected  by  adding 
potash  to  the  liquid.  In  some  countries  all  the  nitrate  of  lime  is 
lost. 

Artificial  nitre  beds  were  at  one  time  formed  in  France  in 
calcareous  soils,  and  in  places  abounding  in  animal  matter.  The 
neighborhood  of  shambles  and  burying  grounds  was  chosen  for 
the  purpose.  The  earth  was  trenched  to  a considerable  depth, 
and  frequently  turned  over  to  expose  fresh  surfaces  to  the  air. 
When  this  supply  was  exhausted,  calcareous  earth  was  exposed 
to  the  draining  of  stables.  The  process  is  tedious,  and  requires 
several  months  for  its  completion. 


SALTS  OF  COMMERCE. 


59 


The  only  country  in  Europe  where  artificial  nitre  heds  are 
still  used  is  Sweden.  There  the  calcareous  earth  is  charged 
with  animal  matter  by  folding  sheep  upon  it.  In  the  United 
States,  in  the  war  of  1812,  a considerable  quantity  of  nitre  was 
manufactured  from  a cave  in  Kentucky.  In  all  these  cases  the 
earth  was  lixiviated,  and  potash  added  to  the  liquor. 

Purification  of  Nitre. — Crude  nitre  contains  about  25  per 
cent,  of  other  substances,  which  may  be  considered  as  impurities. 
These  are  partly  organic,  derived  from  the  animal  and  vegetable 
matter  which  exists  in  the  soil,  and  partly  saline.  In  order  to 
fit  it  for  its  most  important  uses  in  the  arts,  it  requires  to  be 
purified  or  refined.  This  is  effected  by  two  successive  solutions 
and  crystallizations.  In  the  first  solution,  water  having  one-fifth 
of  the  weight  of  the  nitre  is  employed.  This  is  put  in  a copper 
boiler  and  heated.  The  nitre  is  gradually  added  as  the  water 
grows  warm,  and  when  it  boils  the  whole  will  be  dissolved.  The 
organic  matter  being  lighter  than  this  solution,  will  rise  to  the 
surface,  and  may  be  skimmed  off.  In  order  to  facilitate  the  for- 
mation of  a scum,  a small  quantity  of  glue  dissolved  in  water  is 
added  to  the  solution.  The  solution  is  then  poured  into  copper 
basins,  which  are  covered  with  wooden  lids  in  order  to  render 
the  cooling  more  slow.  In  these  basins  a quantity  of  nitre,  equal 
to  the  difference  between  that  which  is  soluble  in  cold  and  in 
boiling  water,  will  crystallize.  A mass  resembling  a sugar  loaf 
is  thus  formed.  This  is  placed  on  shelves  and  permitted  to  drain. 
The  water  which  flows  from  it  still  contains  nitre,  and  the  greater 
part  of  the  saline  impurities.  But  some  of  the  latter  will  also 
remain  adhering  to  the  crystals.  Hence  the  necessity  of  a 
second  solution.  The  quantity  of  water  used  in  this  is  equal  to 
one-third  of  the  weight  of  the  nitre.  Glue  is  also  employed,  and 
any  scum  which  may  form  is  removed.  The  crystallization  is  ef- 
fected as  before ; and  after  the  loaves  have  thoroughly  drained 
the  nitre  is  nearly  pure.  The  liquor  which  drains  off  in  these 
processes  is  concentrated  by  boiling,  and  yields  by  crystallization 
a considerable  quantity  of  nitre. 

A method  has  recently  been  introduced,  which  enables  us  to 
dispense  with  the  second  solution.  The  nitre  being  dissolved  as 


60 


SALTS  OF  COMMERCE. 


before,  in  one-fifth  of  its  weight  of  water,  the  solution  is  treated 
with  glue  and  skimmed.  The  liquor  is  permitted  to  cool  to  1 90°, 
at  which  temperature  it  is  kept ; and  after  about  twelve  hours 
is  poured  into  a vat,  the  bottom  of  which  is  formed  by  two  in- 
clined surfaces.  Here  the  liquid  will  cool  further,  and  the  nitre 
tends  to  crystallize.  The  formation  of  large  crystals  is  prevent- 
ed by  stirring  the  water,  and  the  nitre  which  is  deposited  takes 
the  form  of  a fine  powder.  This  powder  is  placed  in  a vessel 
with  a false  bottom,  and  is  alternately  washed  with  water  and  a 
solution  of  nitre. 

Manufacture  of  Gunpowder. — The  nitrate  of  potassa  is  de- 
composed by  heat.  In  this  decomposition  its  elements  enter  into 
new  combinations,  all  of  which  are  either  vapors  or  gases.  When 
carbon  in  any  of  its  forms  is  mixed  with  the  nitre,  the  decompo- 
sition of  the  latter  is  so  rapid  as  to  be  attended  with  explosion. 
This  explosion,  however,  does  not  take  place  except  at  high  tem- 
peratures. A substance  has  therefore  been  sought  which  pos- 
sesses the  properties  of  taking  fire  at  a low  heat,  and  of  generating 
a high  heat  by  its  combustion.  Sulphur  is  a substance  having 
these  properties,  and  gunpowder  is  a mixture  of  sulphur,  charcoal, 
and  nitre.  The  proportions  do  not  vary  materially  from  75  per 
cent,  of  nitre  and  12^  of  each  of  the  other  substances. 

The  materials  used  in  the  manufacture  of  gunpowder  ought  to 
be  of  the  best  quality.  The  nitre  is  therefore  refined,  the  sul- 
phur purified  by  sublimation,  and  the  charcoal  is  prepared  by  dis- 
tillation in  iron  cylinders.  The  charcoal  which  is  preferred  is 
made  from  the  softest  woods,  and  the  alder,  the  poplar,  and  the 
willow,  are  principally  used  for  the  purpose.  In  Spain  the  char- 
coal is  prepared  from  the  stalks  of  hemp.  The  three  materials 
are  pulverized  separately.  The  charcoal  and  sulphur  are  then 
mixed,  and  the  nitre  is  gradually  added.  The  operations  of  pul- 
verizing and  mixing  were  originally  performed  in  wooden  mor- 
tars. The  pestles  were  also  of  wood,  and  moved  by  machinery. 
At  present,  the  materials  are  ground  and  mixed  in  cylinders  or 
drums,  revolving  on  a horizontal  axis.  So  long  as  they  are  not 
mixed,  the  grinding  is  performed  by  means  of  balls  made  of  an 
alloy  of  copper  ; but  when  the  nitre  is  added,  tin  balls  are  em- 


SALTS  OF  COMMEECE. 


61 


ployed.  In  order  to  lessen  the  danger  of  explosion,  the  mixture 
is  kept  in  a moist  state. 

The  gunpowder  in  this  stage  has  the  form  of  a fine  powder  or 
meal,  in  which  state  it  burns  slowly  for  the  want  of  free  access  of 
air.  It  therefore  requires  to  be  formed  into  grains  when  it  is  to 
be  used  explosively.  These  grains  had  originally  the  form  of 
those  of  rice,  and  were  obtained  by  pressing  the  moist  meal 
through  a sieve.  At  present  spherical  giains  are  preferred. 
These  are  prepared  by  placing  very  dry  meal  in  a revolving  drum. 
A shower  of  drops  of  water  is  permitted  to  fall  upon  the  surface 
of  the  gunpowder  while  the  drum  is  revolving  rapidly.  The 
water  does  not  sink  into  the  dry  mass,  but  the  drops  roll  over 
the  surface  and  each  drop  becomes  the  nucleus  of  a solid  sphere, 
composed  of  moistened  gunpowder.  The  grains  are  then  care- 
fully dried. 

Gunpowder  sometimes  has  a polished  surface  and  is  said  to 
be  glazed.  It  is  glazed  by  the  mutual  friction  of  its  grains, 
which  are  made  to  rub  against  each  other  by  putting  them  into 
a revolving  drum. 

When  the  materials  of  which  gunpowder  is  made  are  good, 
and  it  is  perfectly  dry,  the  whole  mass  is  converted  by  explosion 
into  gas  or  volatile  matter.  Hence  the  quality  of  gunpowder 
may  be  tested  by  flashing  it  from  a sheet  of  white  paper,  on  which 
if  of  good  quality  it  will  leave  no  stain  whatever.  If  the  quality 
be  inferior,  a part  of  the  carbon  will  remain  unconsumed  and 
blacken  the  paper. 

3.  BORAX. 

The  principal  source  of  borax  is  a lake  in  Thibet,  in  which 
impure  crystals  are  found  that  go  by  the  name  of  Tmcal.  This 
contains  beside  the  sub-borate  of  soda,  an  oil  which  is  supposed 
to  be  of  vegetable  origin,  along  with  other  salts  of  the  same  acid. 
In  order  to  purify  the  tincal  it  is  ground  to  powder  and  thrown 
upon  a filtering  cloth.  Here  it  is  washed  with  a dilute  solution 
of  carbonate  of  soda.  The  washing  is  continued  until  the  liquid 


62 


SALTS  OF  COMMERCE. 


runs  off  clear.  By  this  action  the  oil  is  converted  into  a soap 
and  dissolved  in  the  water.  The  matter  which  has  been  washed 
is  then  dissolved  in  boiling  water,  and  to  the  solution  twelve 
parts  of  carbonate  of  soda  are  added  for  each  hundred  of  the 
tincal.  This  serves  to  decompose  the  other  salts.  As  some  of 
these  have  insoluble  bases,  the  solution  requires  to  be  filtered. 
The  filtered  liquor  is  concentrated  by  boiling  and  permitted  to 
crystallize.  The  crystallization  is  performed  in  vessels  having  the 
form  of  a truncated  pyramid,  which  are  lined  with  sheet-lead. 

There  are  springs  in  Tuscany  which  contain  boracic  acid. 
A solid  acid  may  be  obtained  from  these  by  evaporation  and 
crystallization  ; in  this  form  it  is  carried  to  France,  where,  after 
being  redissolved,  it  is  made  to  combine  directly  with  soda  by 
adding  the  carbonate  of  that  alkali  to  the  solution. 


4.  ALUM. 

Alum  was  originally  obtained  from  Bocca  (Edessa)  in  Syria, 
hence  the  best  alum  is  to  this  day  often  called  rock  alum.  The 
manufacture  was  carried  thence  to  Tolfa,  in  the  States  of  the 
Church,  and  it  is  hence  often  called  Roman  alum.  At  these  two 
places  the  double  sulphate  of  alumina  and  potassa  is  formed 
spontaneously.  When  the  chemical  composition  of  alum  was 
discovered,  means  were  found  for  converting  the  sulphate  of 
alumina,  which  is  sometimes  formed  spontaneously  by  the  decom- 
position of  pyrites  in  a slaty  rock,  into  alum.  There  are  also 
some  slates  which  contain  pyrites  that  does  not  decompose  spon- 
taneously. The  decomposition  of  these  may  be  effected  by  arti- 
ficial heat.  It  has  also  been  found  possible  to  form  a sulphate  of 
alumina  by  the  direct  union  of  its  elements,  and  to  convert  this 
into  alum.  When  the  alum  is  already  formed  in  the  rock  it  is 
only  necessary  to  lixiviate  it  and  to  cause  the  solution  to  crys- 
tallize. When  a sulphate  of  alumina  is  formed  spontaneously, 
the  rock  is  lixiviated  and  potassa  added  to  the  solution.  When 
the  pyrites  does  not  decompose  spontaneously,  the  slate  is  formed 
into  heaps  along  with  some  description  of  fuel  by  the  combustion 


SALTS  OF  COMMEKCE. 


63 


of  which  a decomposition  is  effected.  The  whole  mass  is  then  lix- 
iviated. If  wood  have  been  the  fuel,  its  ashes  will  supply  potassa, 
and  when  coal  is  the  fuel,  ammonia  will  have  been  generated  by 
its  combustion,  which  will  have  combined  with  the  sulphate  of 
alumina. 

In  order  to  prepare  alum^by  the  direct  union  of  sulphuric 
acid  and  alumina,  clay  is  roasted  for  several  hours  in  a furnace. 
During  this  time  it  is  continually  stirred,  and  is  thus  prevented 
from  uniting  into  a solid  mass.  The  clay  being  thus  converted 
into  a dry  powder,  is  formed  into  a paste  with  dilute  sulphuric 
acid.  This  paste  is  exposed  for  several  days  to  the  waste  heat  of 
the  furnace.  The  paste  is  then  laid  aside  for  about  a month  ; at 
the  end  of  this  time  it  will  be  found,  that  a sulphate  of  alumina 
has  been  formed  which  may  be  separated  by  washing.  This  may 
be  converted  into  alum  by  the  addition  of  an  alkaline  substance. 
The  paste  is  therefore  lixiviated  and  an  alkaline  carbonate  added 
to  the  solution. 


5.  ACETATE  OF  ALUMINA. 

One  of  the  most  important  uses  of  alum  is  in  the  art  of  dye- 
ing. The  earthy  base  is  precipitated  to  serve  as  a mordant. 
The  sulphuric  acid  being  thus  set  free  is  apt  to  injure  the  tex- 
ture. For  this  reason  it  is  frequently  converted  into  an  acetate 
of  alumina,  before  it  is  employed.  This  acetate  is  prepared  by 
dissolving  three  parts  of  alum  with  one  part  of  acetate  of  lead,  in 
eight  parts  of  water.  A small  quantity  of  chalk  and  pearlash  is 
then  added  to  the  solution.  The  mixture  is  occasionally  stirred, 
and  after  a few  hours'  is  permitted  to  settle.  A clear  liquor  is 
decanted  and  will  contain  a solution  of  the  acetate  of  alumina 
with  sulphate  of  potassa.  The  latter  salt  has  no  effect  either  ad- 
vantageous or  disadvantageous.  It  is  therefore  unnecessary  to 
separate  it.  The  acetate  of  alumina  does  not  crystallize.  The 
solution  is  therefore  preserved  in  a liquid  state. 


64 


SALTS  OF  COMMEKCE. 


6.  SULPHATE  OF  IRON. 

This  salt  is  sometimes  formed  spontaneously  by  the  decom- 
position of  rocks  containing  the  sulphuret  of  iron.  These  rocks 
must  not  contain  clay  or  slate,  otherwise  sulphate  of  alumina  will 
be  generated.  The  sulphuret  of  iron  may  also  be  converted  into 
the  sulphate  by  roasting  it.  There  are  also  sulphurets  of  iron 
found  in  many  places,  which  are  rapidly  converted  into  the  sul- 
phate by  the  action  of  water.  One  of  the  most  remarkable  cases 
of  this  kind  is  at  Strafford,  Yt.  Here  the  sulphuret  of  iron  can 
be  obtained  in  large  quantities.  The  rock  is  broken  into  pieces 
and  piled  into  heaps,  containing  hundreds  of  tons.  Water  is 
sprinkled  over  these  heaps  until  the  sulphuret  is  actually  ignited. 
When  the  fire  has  exhausted  itself,  a stream  of  water  is  directed 
against  the  base  of  the  heap.  This  carries  away  at  first  both  the 
insoluble  and  the  soluble  substances,  but  the  stream  being  caused 
to  fiow  in  a channel  of  small  inclination,  the  former  are  deposited. 
The  clear  liquor  which  contains  the  solution  is  concentrated,  and 
permitted  to  crystallize. 

7.  ACETATE  OF  IRON. 

The  sulphate  of  iron,  which  is  much  used  in  dyeing  black,  is 
liable  to  the  same  objection  as  the  sulphate  of  alumina.  Hence 
for  dyeing  articles  of  the  best  quality,  an  acetate  of  iron  is  often 
prepared.  This  is  manufactured  by  steeping  fragments  of  rusty 
iron  in  vinegar,  or  pyrolignous  acid.  This,  like  the  acetate  of 
alumina,  does  not  crystallize,  and  must  therefore  be  preserved  in 
its  liquid  form. 


IX. 


METALLURGY. 


The  useful  metals  are  found  : native,  usually  in  the  form  of 
alloy  ; combined  with  oxygen  and  other  supporters  of  combustion  ; 
combined  with  sulphur  and  other  combustibles ; and  in  the  state 
of  salts.  These  metallic  compounds  are  usually  mixed  and  ag- 
gregated with  earthy  minerals,  and  to  the  aggregate  we  give  the 
name  of  Ores. 

An  ore  takes  its  name  from  the  metal  which  exists  in  it  in 
greatest  abundance,  except  in  the  case  of  the  precious  metals, 
when  it  takes  its  name  from  the  substance  of  greatest  value. 

Ores  occur  in  alluvial  or  diluvial  formations;  in  beds  in 
stratified  rocks  ; and  in  veins  that  traverse  both  stratified  and 
unstratified  rocks. 

To  obtain  the  useful  metals  from  their  ores,  various  processes 
are  necessary,  which  may  be  arranged  under  the  three  heads  of 
Mechanical,  Physical,  and  Chemical. 


1.  MECHANICAL  PROCESSES. 

1. — Ticking  and  Sorting. 

When  ores  have  been  extracted  from  the  mine,  they  are  in 
the  first  place  picked  and  sorted.  For  this  purpose  they  are 
broken  with  a hammer,  in  such  manner  as  to  expose  the  interior 
5 


66 


METALLUEGY. 


of  the  mass,  and  separate  any  external  earthy  matter.  The 
broken  pieces  are  usually  arranged  in  three  parcels,  the  first  of 
which  is  rich  enough  to  be  worked  ; the  second,  undergoes  a sec- 
ond picking  and  sorting ; the  third  is  too  poor  to  be  profitably 
worked. 

2. — Stamping  and  Crushing. 

Stamping  is  performed  by  machines  moved  by  water,  or  other 
convenient  power.  The  apparatus  is  composed  of  a number  of 
heavy  beams,  set  vertically  in  a frame.  From  each  beam  a tooth 
or  caoi  projects.  An  axle  revolves  in  the  neighborhood  of  the 
beams,  on  which  teeth  are  arranged  in  the  form  of  a helix.  These 
teeth  taking  hold  of  the  cams  on  the  beams,  raise  them  in  suc- 
cession, and  when  by  the  revolution  of  the  axle,  the  teeth  cease 
to  lock,  the  beams  fall  by  their  own  weight.  The  beams  are  shod 
with  iron,  and  the  ore  is  laid  on  a bed  of  iron  or  stone.  The  bed 
may  be  dry,  in  which  case,  the  fineness  of  the  ore  is  regulated  by 
sieves  ; or  it  may  be  placed  in  a trough,  through  which  water  is 
continually  flowing.  The  fineness  of  the  ore  is  in  this  case  regu- 
lated by  the  force  of  the  current. 

Crushing  is  performed  by  causing  the  ore  to  pass  downwards 
between  rollers.  Of  these,  there  are  several  pairs,  the  uppermost 
of  which  have  the  greatest  space  between  them.  After  passing 
the  upper  rollers  the  ore  falls  upon  a sieve,  whose  bottom  is  in- 
clined, and  which  is  continually  shaken  by  the  same  force  which 
turns  the  rollers. 

3. — Washing  and  Concentration. 

When  ore  in  fine  powder  is  mixed  by  agitation  with  water,  the 
heavier  particles  sink  first,  and  the  less  dense  may  be  removed 
by  discharging  the  water  before  it  ceases  to  be  turbid.  As  me- 
tallic is  usually  heavier  than  earthy  matter,  the  greater  part  of 
the  latter  may  by  a process  founded  on  this  principle,  be  separa- 
ted from  the  former.  Washing  may  be  performed  by  hand  in 
bowls,  or  even  in  a common  frying  pan,  and  various  machines 


METALLUEGY. 


67 


have  been  planned  for  performing  it  on  a large  scale . The 
character  of  the  machine  will  differ  according  to  the  nature  of  the 
metal  contained  in  the  ore. 

In  concentration,  the  powdered  ore  is  mixed  by  agitation  with 
a large  quantity  of  water,  and  then  left  at  rest.  For  the  same 
reason  as  before,  the  metallic  portions  tend  to  sink  first,  and  the 
earthy  matter  last.  The  water  is  removed  after  it  has  become  clear, 
and  the  paste  which  remains  beneath  is  separated  by  horizontal  cut- 
ting into  three  portions.  The  upper  portion  is  rejected,  the  mid- 
dle portion  is  concentrated  a second  time,  and  the  lower  portion 
is  ready  for  the  subsequent  processes. 

2.  PHYSICAL  PROCESS. 

Roasting. 

Roasting  is  the  only  important  physical  process.  It  consists 
in  exposing  the  stamped  and  washed,  or  concentrated  ore,  to  a 
heat  sufiicient  to  separate  its  volatile  parts.  In  this  way,  water, 
carbonic  acid,  sulphur,  arsenic,  &c.,  may  be  separated  from  the 
metals  with  which  they  are  combined. 

Roasting  of  ores  that  do  not  contain  pyrites  in  large  quanti- 
ties, may  be  performed  in  large  heaps,  by  placing  the  ore  and  fuel 
in  alternate  layers  ; in  kilns  composed  of  three  walls  ; in  kilns  re- 
sembling lime-kilns  ; and  in  reverberatory  furnaces.  In  some 
cases,  arsenic  and  sulphur  are  separated  in  quantities  sufficient 
to  defray  the  expense  of  collecting  them.  For  this  purpose,  the 
kilns  may  be  placed  under  sheds,  or  the  deposit  may  be  formed 
in  the  chimneys  of  the  reverberatory  furnaces. 

Pyritical  ores  may  be  roasted  by  means  of  a single  layer  of 
fuel  forming  the  base  of  a large  pyramidal  heap.  The  sulphur 
which  is  separated  by  the  combustion  of  the  fuel  from  the  lower 
part  of  the  heap,  serves  as  fuel  for  the  upper  portions. 


68 


METALLURGY. 


3.  CHEMICAL  PROCESSES. 

1. — Smelting. 

In  smelting,  the  earthy  matter  of  the  ore  is  converted  by 
fusion  into  a vitreous  substance.  In  some  cases  the  earthy  mat- 
ter is  fusible  without  addition.  More  frequently,  it  becomes  ne- 
cessary to  add  some  other  earthy  mineral,  which  is  called  a Flux. 
When  the  ore  contains  little  or  no  silica,  some  silicious  mineral 
must  be  added,  with  or  without  another  flux.  When  the  ore 
abounds  in  silica,  limestone,  or  quicklime,  is  added.  The  vitreous 
matter  is  less  dense  than  the  reduced  metal,  and  they  do  not  mix 
with  each  other. 


2. — Reduction. 

To  separate  oxygen  from  a metal,  it  is  heated  in  contact  with 
carbonaceous  matter.  Charcoal  and  coke  are  employed  for  this 
purpose,  and  in  some  cases  wood  or  even  coal.  The  processes  of 
smelting  and  reduction,  although  very  difirerent  in  principle  are 
performed  together  in  furnaces. 

The  furnaces  in  which  ore  is  smelted  and  reduced,  are  of  two 
kinds.  In  the  first,  air  is  supplied  to  the  burning  fuel  by  the 
draught  of  a chimney.  These  are  called  air  or  wind  furnaces. 
In  operations  on  a small  scale,  the  ore  may  be  placed  in  crucibles 
On  the  large  scale  the  ore  is  placed  on  a hearth  in  a chamber, 
which  is  placed  between  the  furnace  proper,  and  the  chimney. 
A furnace  of  this  character  is  styled  Reverberatory. 

In  the  second  kind  of  furnaces,  air  is  supplied  by  a blowing 
machine.  Of  these,  the  most  familiar  is  the  common  bellows. 
To  furnaces  thus  supplied  with  air,  the  epithet  of  Blast  may  be 
given  as  the  generic  name.  They  may  be  of  various  kinds  from  the 
Forge  fire.^  which  is  kindled  in  a shallow  cavity,  to  the  blast  fur- 
nace used  in  making  Fig  iron^  some  of  which  have  been  70  feet 
in  height. 


METALLUKGY. 


69 


1.  METALLUKGY  OF  IKON. 

1. — Ores  of  Iron. 

All  the  useful  ores  of  iron  are  either  oxides  or  carbonates. 
The  protoxide  probably  occurs  in  the  crystallized  ores  of  Elba, 
and  at  Peru,  in  the  State  of  N.  Y.  The  magnetic  oxide  is  found 
in  grains,  and  in  crystals  aggregated  in  masses  in  primitive  rocks, 
the  usual  form  of  its  crystals  being  the  octoedron. 

The  peroxide,  occurs  in  the  form  called  from  its  appearance 
micaceous  and  specular  iron  ; and  in  combination  with  water  in 
the  haematites,  and  the  bog  and  meadow  ores. 

The  carbonate  of  iron  occurs  in  crystals,  and  crystalline  mas- 
ses of  great  purity.  It  also  occurs  mixed  with  carbonate  of  lime, 
clay,  or  other  earthy  matter,  in  some  coal  formations,  where  it  is 
known  as  Iron-stone. 

2. — History. 

Iron  is  mentioned  in  the  oldest  writings,  both  sacred  and  pro- 
fane. It  is,  however,  among  the  most  difficult  of  the  metals  to 
obtain  from  its  ores,  and  the  methods  are  so  far  from  perfect  that 
they  are  receiving  improvements  almost  daily.  It  would  appear 
that  the  first  iron  used  by  man  was  found  native,  as  it  is  still  oc- 
casionally found  at  the  present  day,  and  is  ascribed  to  meteoric 
origin.  In  this  state,  it  appears  from  a passage  in  scripture,  to 
have  been  abundant  in  Palestine.  The  earliest  workers  of  iron 
from  its  ore,  seem  to  have  been  the  Chabybes,  a nation  of  Asia 
Minor,  called  Chaldeans  by  Xenophon,  in  whose  original  seats 
iron  is  still  worked. 

From  this  people,  the  Grreeks  learnt  the  art,  if  not  of  making 
iron,  certainly  of  making  steel,  as  appears  from  the  Greek  name 
of  that  substance.  Elis  in  Greece,  was  the  seat  of  an  extensive 
iron  manufacture,  and  Homer  refers  to  a traffic  in  which  the  iron 
of  Greece  was  exchanged  for  the  bronze  of  the  Tyrrhenians. 

The  art  of  smelting  iron,  was  carried  by  Greek  colonies 


70 


' METALLUEGY. 


throughout  the  shores  of  the  Mediterranean,  and  by  one  of  them, 
the  mines  of  Elba  were  opened  3 or  400  years  B.  C.  These 
mines  are  still  worked,  the  ores  being  smelted  in  Tuscany  and 
Catalonia,  by  methods  apparently  identical  with  the  ancient 
Steel  was  probably  obtained  accidentally,  and  the  iron  in  the 
original  process  passes  through  a state  of  combination  identical 
with  steel.  Steel  may  also  be  obtained  with  certainty  from  the 
crystallized  carbonate  of  iron. 

Cast-iron  is  usually  said  to  have  been  accidentally  discovered 
in  Alsace,  towards  the  close  of  the  15th  century,  but  it  would  ap- 
pear that  the  Chinese  have  possessed  the  art  of  making  it  for 
ten  or  twelve  centuries. 


3. — Blooming. 

Wrought-iron  maybe  obtained  directly  from  its  ores.  Those 
best  suited  for  the  purpose,  are  rich,  and  contain  earthy  matter 
which  when  combined  with  a small  quantity  of  oxide  of  iron,  is 
easily  fusible. 

The  ore,  after  being  picked  and  sorted,  is  stamped  into  a 
coarse  powder.  The  apparatus  employed  is  a forge  fire,  the 
fuel  charcoal.  Some  ores  may  be  reduced  in  a common  smith’s 
forge,  but  one  of  larger  size  and  specially  constructed,  is  generally 
employed.  The  fire  is  lighted  in  a shallow  cavity  in  the  hearth 
of  the  forge,  and  is  heaped  into  a conoidal  mass  against  the  wall. 
The  blowing  apparatus  is  a pair  of  bellows,  each  composed  of 
two  pyramidal  boxes  of  wood,  usually  driven  by  a water-wheel, 
and  acting  alternately.  When  the  heap  of  charcoal  is  fully  igni- 
ted the  bellows  are  set  in  action,  and  a layer  of  ore  is  strewn 
over  the  fuel.  Upon  this  another  layer  of  charcoal  is  laid,  which 
is  followed  by  another  layer  of  ore,  until  as  much  as  can  be  acted 
upon  has  been  introduced. 

The  ore  being  heated,  the  earthy  matter  combines  with  a part 
of  the  oxide  of  iron  to  form  a compound  known  from  its  charac- 
ter as  the  vitreous  oxide.  The  rest  of  the  oxide  of  iron,  enveloped 
in  an  atmosphere  of  carbonic  oxide  is  reduced,  and  the  result- 
ing iron  in  contact  with  carbon,  forms  with  it  a compound  analo- 


METALLUEGY. 


71 


gous  to  steel.  To  separate  the  carbon,  the  iron  is  raised  up,  and 
exposed  to  the  blast,  under  whose  action  the  carbon  burns  away. 
The  iron  finally  subsides  into  the  cavity  of  the  hearth,  where  by 
pressure  it  takes  the  form  of  a spongy  mass,  whose  cavities  are 
filled  with  the  vitreous  oxide,  and  which  is  called  a Loop.  The 
loop  being  taken  from  the  fire,  is  beaten  on  an  iron  fioor  with 
wooden  mallets,  by  whose  action  a large  proportion  of  the  vitreous 
oxide  is  separated.  It  is  then  replaced  in  the  furnace,  and  brought 
again  to  a welding  heat. 

The  loop  is  next  placed  on  an  anvil  and  beaten  with  the  Forge 
Hammer  into  the  form  of  an  irregular  polygonal  prism,  which  is 
called  the  Shingle.  The  forge-hammer  is  made  of  cast-iron,  hav- 
ing a shape  somewhat  resembling  the  letter  D.  It  weighs  several 
cwts.,  and  is  mounted  on  one  end  of  a strong  beam  of  wood,  the 
opposite  end  of  which  rests  on  gudgeons.  To  lift  it,  an  axle 
driven  by  a water-wheel,  revolves  close  to  the  beam,  having  cams 
projecting  from  it  which  apply  themselves  near  the  head  of  the 
hammer,  and  lift  it  with  such  force  as  to  throw  it  against  a beam 
or  wooden  spring,  whence  it  rebounds  towards  the  anvil. 

The  shingle  is  reheated  and  beaten  into  the  form  of  a paral- 
lelopiped  called  the  Bloom.^  from  which  the  process  takes  its 
name. 

The  bloom,  or  as  much  of  it  as  is  sufficient  to  form  a bar  of 
the  desired  size,  was  formerly  thrice  reheated  and  beaten  to  draw 
it  into  a bar.  At  the  present  time,  blooms  are  often  reheated 
only  once,  and  are  drawn  into  bars  by  passing  them  between  roll- 
ers. The  reheating  of  the  bloom  is  also  performed  in  an  oven 
or  reverberatory  furnace,  instead  of  a forge  fire.  By  both  me- 
thods much  fuel  and  labor  may  be  saved. 

Poor  ores  may  also  be  converted  directly  into  iron.  Instead 
of  a forge  fire,  a furnace,  whose  depth  is  three  or  four  times  as 
great  as  its  diameter,  is  employed.  The  ore,  mixed  if  necessary 
with  a flux,  is  placed  in  the  cavity  with  charcoal  in  alternate 
strata.  When  the  charcoal  is  burnt  away,  a loop  may  be  found 
in  the  cavity,  but  it  often  contains  a liquid  mass  of  carburet  of 
iron.  This  process  is  no  otherwise  interesting,  than  as  that  in 
which  cast-iron  was  originally  discovered. 


72 


METALLUKGY. 


4. — Cast-Iron. 

Cast-iron  is  manufactured  in  a furnace  to  which  the  name  of 
Blast  Furnace  is  usually  restricted. 

A blast  furnace  has  usually  the  external  form  of  a square 
truncated  pyramid.  The  height  has  varied  from  18  ft.  to  70  ft. 
The  pyramid  is  usually  pierced  on  all  its  sides  with  arches,  which 
support  the  masonry  above  ; one  of  these  afibrds  a place  of  dis- 
charge for  the  metal  and  vitrified  earths.  Through  the  others, 
pipes  pass  that  convey  the  air  from  the  blowing  apparatus.  The 
cavity  of  the  furnace  is  inclosed  in  a lining  of  fire-brick,  or  re- 
fractory stone.  The  cavity  has  a shape  which  may  be  described, 
by  supposing  two  truncated  cones  to  be  joined  to  each  other  at 
their  greater  bases,  and  that  the  lower  cone  rises  from  a square 
truncated  pyramid,  differing  but  little  from  a prism.  The  lower 
or  pyramidal  portion  is  called  the  Crucible;  the  wide  space  at 
the  junction  of  the  two  cones,  the  Boshes ; the  opening  at  top, 
the  Trundle-Head.  The  space  between  the  outer  pyramidal  wall 
and  the  lining  is  filled  with  sand,  for  the  purpose  of  preventing 
the  outer  wall  from  being  broken  by  the  expansion  of  the  lining. 

The  blowing  apparatus  was  originally  composed  of  two  wooden 
bellows,  like  those  described  in  the  preceding  section.  Various 
other  forms  were  subsequently  employed,  until  finally  a double 
acting  cylinder  of  cast-iron  has  superseded  all  others. 

So  long  as  bellows  were  used,  the  quantity  of  air,  and  the 
pressure  at  which  it  was  introduced  were  limited.  More  iron 
was  therefore  made  in  winter  than  in  summer,  because  the  vol- 
ume of  air  being  limited  by  the  power  of  the  blowing  apparatus, 
the  absolute  quantity  was  greater  in  cold  weather  than  in  warm. 
With  a double  acting  cylinder  propelled  by  a steam  engine,  the 
volume  of  air  can  be  increased  beyond  what  can  possibly  be 
needed.  In  this  way  an  equal  weight  of  air  can  be  introduced, 
whether  its  temperature  be  high  or  low.  It  has,  therefore,  be- 
come possible  to  introduce  air  artificially  heated.  This  has  been 
done,  and  has  been  attended  with  great  advantages. 

1.  The  quantity  of  iron  made  will  be  equal,  whatever  be  the 
external  temperature. 


METALLURGY. 


73 


2.  The  height  of  the  furnace  is  limited  not  by  the  force  of  the 
blast,  but  by  the  nature  of  the  fuel.  With  charcoal  made  from 
soft  wood,  it  may  be  as  great  as  28  or  30  ft.,  with  charcoal  from 
hard  wood,  from  36  to  40  ft.,  and  with  coke  from  40  to  48  ft. 

By  an  increase  in  the  dimensions  of  the  furnace,  the  interior 
may  be  kept  at  a higher  temperature  with  a given  consumption 
of  fuel.  In  this  way  either  more  iron  may  be  made,  or  iron  of  a 
higher  quality. 

Cast-iron  may  be  either  composed  of  an  aggregate  of  separate 
grains  of  carbon  and  iron,  of  a definite  compound  of  carbon  and 
iron,  of  a white  color,  or  of  a mixture  of  iron,  carbon  and  differ- 
ent carburets  of  iron.  The  highest  quality  or  No.  1,  is  of  the 
first  description,  and  No.  3 is  the  definite  white  compound  of 
iron  and  carbon,  usually  called  forge-pig^  because  it  is  of  little 
use  except  to  convert  into  wrought  iron.  To  obtain  the  highest 
quality  of  No.  1,  the  heat  of  the  furnace  must  be  sufiicient  to  melt 
wrought  iron,  and  the  liquid  metal  must  cool  slowly.  By  rapid 
cooling  the  highest  quality  may  be  rendered  white. 

3.  The  consumption  of  fuel  may  be  lessened. 

4.  Raw  coal  and  wood  may  be  used  in  part,  instead  of  char- 
coal and  coke ; and  anthracite,  which  could  not  be  used  when  the 
blast  was  not  heated,  may  be  employed  as  fuel. 

To  set  a blast-furnace  in  action,  a fire  is  lighted  under  one 
of  the  arches  for  the  purpose  of  drying  the  furnace.  This  fire  is 
made  of  brush  or  other  fuel  burning  with  much  flame.  A fire  is 
next  lighted  in  the  bottom  of  the  furnace,  called  the  Hearth. 
The  hearth  is  composed  of  a large  flat  stone,  and  inclosed  on  the 
side  whence  the  metal  is  to  be  withdrawn,  by  the  Dam  and 
Tymp.  The  dam  rests  on  the  hearth,  and  was  formerly  of  stone. 
It  is  now  usually  a hollow  block  of  cast-iron,  kept  from  melting 
by  the  passage  of  a stream  of  water  through  it.  Between  the 
dam  and  tymp  is  an  opening,  through  which  the  excess  of  vitre- 
ous matter  may  flow. 

Under  the  dam  is  a passage  for  the  flow  of  the  metal,  which 
is  usually  closed  with  a plug  of  tempered  clay.  To  draw  off  the 
metal,  the  furnace  is  tapped  by  breaking  through  the  clay  with 
an  iron  tool,  pointed  with  steel.  When  the  furnace  has  been 


74 


METALLUEGY. 


thoroughly  dried,  fuel  is  gradually  added  to  that  in  the  hearth, 
until  the  whole  cavity  is  filled  with  ignited  fuel.  The  blowing 
apparatus  is  then  set  in  action,  and  the  charging  of  the  furnace 
commences,  by  throwing  charges  in  at  the  trundle-head.  A 
charge  is  composed  of  a constant  quantity  of  charcoal,  and  a mix- 
ture of  ore  and  flux  in  constant  proportions.  The  quantity  of 
this  mixture  is  small  as  first,  and  is  gradually  increased  until  the 
furnace  assumes  a regular  state  of  working,  and  can  be  tapped  at 
regular  intervals  of  12  hours.  The  charges  are  repeated  at  regu- 
lar intervals,  until  the  stock  of  materials  is  exhausted,  or  the 
furnace  ceases  to  be  in  working  order. 

As  the  charge  descends  in  the  furnace,  the  earthy  part  of  the 
ore,  the  flux,  and  a part  of  the  oxide  of  iron,  unite  to  form  a glass 
called  the  Cinder.  The  cinder  being  liquid  descends  to  the 
hearth,  where  the  heat  is  suflacient  to  keep  it  fluid.  The  oxide 
of  iron  enveloped  in  an  atmosphere  of  carbonic  oxide  is  reduced, 
and  being  in  contact  with  carbon,  unites  with  it,  thus  becoming 
fusible.  The  carburet  of  iron  melts,  and  follows  the  cinder  to 
the  hearth,  where  from  its  superior  density  it  sinks  beneath  it, 
and  is  protected  by  it  from  the  blast.  A part  of  the  earths  also 
is  reduced,  and  their  bases  united  with  the  carburet  of  iron. 

Cast-iron  is  therefore,  a very  complex  substance,  containing 
not  merely  carbon  and  iron  in  various  modes,  but  also  the  me- 
tallic bases  of  earths,  and  the  metalloid  silicon.  Its  quality  is, 
perhaps,  as  much  affected  by  the  character  of  the  earthy  bases 
with  which  it  is  alloyed,  as  by  any  other  circumstance. 

To  receive  the  iron  drawn  from  the  furnace  by  tapping, 
trenches  are  cut  in  a floor  of  sand.  One  of  these  is  of  considera- 
ble length  ; the  others  are  arranged  at  right  angles  to  it,  and  hold 
each  about  1 cwt.  of  iron.  The  iron  which  flows  into  the  long 
trench,  and  thence  into  those  at  right  angles,  is  called  the  soiv 
andy?zg-5.  Hence  the  name  oi pig-iron. 

Castings  may  be  made  of  pig-iron  as  it  flows  from  the  blast- 
furnace by  receiving  it  into  moulds.  They  are  more  usually 
made  from  remelted  pig-iron.  Pig-iron,  and  old  castings,  may 
be  melted  for  the  purpose,  either  in  reverberatory  furnaces  or  in 
low  blast  furnaces,  called  Cupolas. 


METALLURGY. 


75 


The  moulds  may  be  made  of  three  dilFerent  materials,  called 
green  sand,  dry  sand,  and  loam.  Moulds  of  either  description  of 
sand  are  made  in  iron  frames  or  boxes,  by  the  aid  of  a pattern 
made  of  wood  or  metal.  The  box  is  of  such  form  that  the  mould 
may  be  made  in  at  least  two  pieces,  so  that  it  may  be  opened  to 
remove  the  pattern.  The  pattern  being  supported  within  the 
box,  sand  is  rammed  around  it.  The  surfaces  at  which  the  box 
is  to  opened,  are  dusted  with  powdered  coke  to  prevent  adhesion. 
After  the  several  parts  of  the  box  have  been  filled  with  sand,  the 
box  is  opened  and  the  pattern  is  taken  out,  leaving  a cavity  hav- 
ing exactly  its  own  shape.  Grreen-sand  moulds  contain  a small 
quantity  of  water  and  of  clay,  to  render  the  sand  adhesive.  The 
presence  of  water  may  be  dangerous.  Hence,  for  large  castings, 
the  sand  is  mixed  with  a larger  quantity  of  tempered  clay,  and 
the  water  is  evaporated  by  placing  the  moulds  in  a heated  oven. 

Every  mould  must  have  at  least  two  openings,  one  for  the  ad- 
mission of  the  heated  metal,  the  other  for  the  escape  of  air  and 
vapor.  The  discharge  through  the  latter  may  be  accelerated  by 
setting  fire  to  the  hydrogen,  which  escapes  from  it.  This  hydro- 
gen is  furnished  by  the  decomposition  of  the  water  of  the  mould. 

Loam  moulds  are  made  by  laying  brick  in  an  earth  of  that 
character,  plastering  the  brick  with  the  same  material,  and  giving 
to  the  interior  cavity  of  the  mass  the  shape  required.  The  mould 
is  finally  dried  by  lighting  a fire  within  it. 

5. — Refining. 

In  refining,  cast-iron  is  converted  into  wrought-iron.  The 
apparatus  is  a forge  fire  similar  to  that  used  in  blooming,  except 
that  an  opening  is  left  in  the  wall,  over  the  cavity  of  the  hearth, 
for  the  purpose  of  introducing  the  pig  of  iron.  The  fuel  is  char- 
coal, and  the  [chemical  part  of  the  process  consists  in  burning 
away  the  carbon.  The  metallic  iron  collects,  with  vitreous  oxide, 
in  the  hearth,  in  the  form  of  a loop.  The  subsequent  processes 
are  the  same  as  in  blooming. 

Refining  may  be  used  to  advantage  wherever  large  bodies 
of  woodland  exist  The  absolute  cost  of  refined  iron  in  fuel 


76 


METALLURGY. 


and  labor,  is  less  than  that  of  bloomed,  but  it  may  be  impractica- 
ble to  employ  the  process  of  refining. 

A blast  furnace  in  which  charcoal  is  used,  will  require  all  the 
wood  that  can  be  furnished  by  successive  growth  on  7000  acres 
of  woodland.  It  will  supply  material  for  5 or  6 refineries,  each 
of  which  requires  at  least  2000  acres  of  woodland  to  keep  it  in 
action. 

Refined  iron  made  from  ore  of  equal  quality,  is  better  than 
bloomed  iron,  being  more  homogeneous  and  free  from  wiry  fibres 
of  steel.  But  as  cast-iron  can  be  made  from  ores  very  inferior  to 
any  that  can  be  used  in  blooming,  and  as  any  cast-iron  may  be 
refined,  the  average  quality  of  refined  is  inferior  to  that  of  bloomed 
iron. 

If  the  pig  iron  contain  the  bases  of  earths,  they  are  oxydated 
in  the  process  of  refining,  and  concur  to  form  the  vitreous  oxide 
which  collects  in  the  cavity  of  the  loop. 

7. — Rolling  and  Slitting. 

To  obtain  small  bars  either  round  or  rectangular,  by  heating 
in  a forge  fire  and  beating  with  the  forge  hammer,  would  be  very 
costly.  Hence  only  large  bars  are  made  either  in  the  processes 
of  blooming  or  of  refining.  To  reduce  these  bars  to  a smaller 
size  they  are  heated  in  an  oven  to  a welding  heat,  and  are  then 
passed  between  rollers  driven  by  water  or  steam.  To  make  round 
iron,  a large  round  bar  is  passed  through  grooves  cut  opposite  to 
each  other  in  the  rollers,  each  having  the  section  of  a semicircle. 
The  grooves  diminish  in  size,  in  succession,  until  the  bar  acquires 
the  proper  size.  To  make  small  rectangular  bars,  a large  flat  bar 
is  drawn  between  rollers  having  rectangular  grooves  cut  in  them 
in  such  a manner  that  the  projection  on  one.  roller  corresponds  to 
the  cavity  in  the  other.  The  bar  is  thus  slit  into  many  pieces  at 
a single  operation. 

This  method  is  now  of  little  importance  except  historically. 

6. — Puddling. 

When  coke  is  used  instead  of  charcoal  in  a refinery  fire,  the 
cast-iron  does  not  lose  enough  of  its  carbon  to  cease  to  be  fusi- 


METALLURGY. 


77 


ble.  It  therefore  will  not  collect  in  a loop,  or  come  to  nature. 
The  carbon  may  be  removed  by  heating  cast-iron  in  a reverbe- 
ratory furnace,  with  free  access  of  air.  Both  methods  are  now 
combined  in  the  process  of  puddling.  Pig-iron  is  first  heated 
with^coke  in  a forge  fire.  The  forge  fire  is  now  made  so  large  as 
to  admit  of  several  nozzles  or  tuyeres.^  for  the  admission  of  the 
blast,  and  from  three  to  nine  pigs  may  be  acted  upon  at  a time. 
The  melted  iron  is  removed  by  tapping  the  cavity  of  the  hearth, 
and  is  received  on  a plate  of  cast  iron,  where  it  cools  rapidly.  To 
break  it  to  pieces  and  render  it  brittle,  it  is  sprinkled  with  wa- 
ter while  red-hot.  The  broken  pieces  are  then  stamped. 

The  stamped  iron  is  placed  in  a reverberatory  furnace,  on  a 
hearth,  composed  at  first  of  sand,  and  afterwards  of  vitreous  ox- 
ide. The  hearth  has  also  been  made  of  rich  magnetic  ores  of 
iron.  The  fuel  is  bituminous  coal. 

When  the  iron  has  melted,  it  is  stirred  with  iron  tools,  and 
free  access  of  air  is  permitted.  The  carbon  is  thus  burnt  away, 
the  bases  of  the  earths,  and  some  of  the  iron  are  oxydated,  and 
unite  to  form  the  vitreous  oxide.  Finally,  the  iron  ceases  to  be 
fusible,  and  becomes  malleable.  It  is  at  this  time  in  the  form  of 
small  grains,  which,  if  pressed  together  adhere,  and  form  balls  or 
loops.  A thin  bar  of  iron  is  introduced  to  form  the  nucleus  of 
each  ball,  and  serves  as  a handle.  The  balls  were  formerly  with- 
drawn in  succession,  and  passed  between  rollers,  having  grooves 
diminishing  in  succession,  until  the  required  form  of  bar  be 
given. 

In  rolling,  the  vitreous  oxide  is  pressed  towards  one  end  of 
the  bar,  whence  a part  of  it  exudes,  but  cannot  be  entirely  sepa- 
rated. The  forge  hammer  removes  the  vitreous  oxide  complete- 
ly, but  is  so  slow  in  its  action,  that  a ball  could  not  be  both  ham- 
mered and  drawn  without  being  reheated.  The  advantages  of 
both  hammering  and  rolling  have  been  united,  by  the  use  of 
hammers  weighing  several  tons,  and  moving  with  great  rapidity. 
After  these  have  compressed  the  balls  to  the  utmost,  they  still 
contain  heat  enough  to  permit  them  to  be  rolled. 

Puddled  iron  is  often  of  poor  quality ; because  iron  may  be 
passed  between  rollers,  even  although  it  would  fiy  to  pieces  un- 


78 


METALLURGY, 


der  the  hammer.  To  render  it  merchantable,  the  bars  are  cut 
into  pieces  of  from  6 to  18  inches  in  length.  Several  of  the  bars 

piled  one  upon  the  other.  These  piles  are  placed  side  by 
side,  and  end  to  end,  on  the  hearth  of  a reverbatory  furnace. 
On  this  layer  of  piles  another  is  placed  at  right  angles.  In  the 
furnace  the  piles  are  brought  to  a |vhite  heat,  by  which  a large 
quantity  of  vitreous  oxide  is  formed,  of  which  exudes  like 
sweat  from  the  pile.  The  piles  are  then  passed  through  rollers 
of  higher  finish  than  the  puddle  rolls,  and  become  merchant-bars. 

In  both  puddling  and  reheating,  the  vitreous  oxide  is  pressed 
by  the  rolls  towards  one  end  of  the  bar.  These  ends  are  cut  off, 
piled,  reheated,  and  rolled,  furnishing  iron  of  better  quality. 
Smaller  scrap  is  heated  in  a puddling  furnace,  rolled  into  bars, 
cut,  piled,  reheated,  and  again  rolled,  yielding  iron  of  still  higher 
quality. 

Iron  made  by  the  process  of  puddling  with  bituminous  coal, 
from  American  charcoal-made  pig  iron,  is  of  better  quality  than 
any  imported. 

The  best  iron  made  in  England  is  used  wholly  in  the  manu- 
facture of  chain  cables,  and  is  never  seen  in  this  country  in  its 
original  form.  The  pig  iron  is  melted  in  a forge  fire,  with  char- 
coal, run  into  plate  iron,  stamped,  puddled  with  bituminous  coal, 
cut,  piled,  and  reheated. 


8. — Steel. 

Steel;  as  has  been  seen,  may  be  obtained  directly  from  ores 
containing  crystallized  carbonate  of  iron.  The  greater  part  of 
the  steel  of  commerce,  however,  is  made  from  bar  iron,  and  the 
art  is  most  extensively  practised  in  England.  The  material 
there  employed  is  made  solely  at  a few  forges  in  Sweden.  Rus- 
sia formerly  yielded  iron  for  this  purpose,  but  it  is  no  longer  ex- 
ported. It  has  been  supposed  that  the  properties  of  the  iron  of 
these  forges  depended  on  their  extreme  purity  ; but  this  idea 
has  been  set  aside,  and  the  precise  reason  of  its  superior  value 
remains  to  be  investigated.  One  forge  in  New  Jersey  furnishes 
iron,  from  which  steel  of  the  best  quality  may  be  made  ; but,  ex- 


METALLURGY. 


79 


cept  in  case  of  a war  with  England,  this  iron  is  of  too  much 
value  for  other  purposes,  to  he  employed  in  making  steel. 

In  making  steel,  the  bar  iron  is  placed  in  layers,  in  a rectan- 
gular oven,  and  completely  imbedded  in  powdered  charcoal.  In 
this  it  is  exposed  to  a red  heat  for  several  days.  When  removed, 
it  is  found  that  the  surface  has  distended  and  risen  from  the  bar, 
giving  it  an  appearance  which  entitles  it  to  the  name  of  Blistered 
Steel. 

Blistered  steel  is  richest  in  carbon  at  the  surface.  To  render 
it  homogeneous,  it  may  be  brought  to  a welding  heat,  and  beaten 
with  Tilt  Hammers,  when  it  is  called  Tilted  Steel.  It  is  now 
more  usually  melted  in  crucibles,  with  the  addition  of  powdered 
charcoal  and  glass.  The  latter  preserves  it  from  burning,  by 
contact  with  air.  When  melted,  it  is  cast  into  ingots,  in  moulds 
of  wrought-iron.  The  ingots  are  drawn  into  bars  by  the  tilt 
hammer,  or  by  rollers. 

Steel  will  combine  when  liquid,  with  a small  portion  of  silver. 
The  compound  is  harder  than  common  cast-steel. 

A kind  of  steel  called  Wootz,  is  brought  from  India.  On 
analysis,  it  appears  to  contain  aluminum. 

Silver  steel  is  distinguished  by  oval  spots,  and  wootz  by  strim 
of  different  lustre  on  its  surface. 

The  same  steel  may  have  different  degrees  of  hardness  and 
elasticity  given  it  by  Tempering.  Tempering  consists  in  heating 
the  steel  to  different  temperatures,  and  cooling  it  at  different 
heats.  When  heated  to  the  highest  degree  and  suddenly  cooled, 
it  is  hard  and  brittle,  when  moderately  heated  and  slowly  cooled, 
it  is  soft  and  elastic. 

The  proper  degree  of  heat  was  formerly  judged  of,  by  the 
color  the  steel  assumed.  It  is  now  known,  that  the  temperatures 
necessary  for  the  purpose  are  included  between  the  boiling  points 
of  water  and  mercury.  Hence,  tempering  is  now  performed  by 
heating  the  articles  of  steel  in  a bath  of  mercury,  and  withdraw- 
ing them  in  succession  as  the  proper  temperature  is  reached. 

Before  this  discovery,  the  manufacture  of  particular  articles 
was  restricted  to  particular  places,  and  the  art  often  died  with 
the  workman.  At  present  it  may  be  considered  universal. 


